Is there any empirical evidence to back up the claim that following the conventional definition of veganism leads to greater overall harm reduction rather than thinking in more consequential terms ? Also, unless I am mistaken, the utilitarian argument for rule-of-thumb applies in a context where we are either faced with an inability to determine the right course of action (owing to uncertainties in estimates of potential outcomes, say) or when the decision that emerges from such a calculation runs strongly counter to common sense.

I don’t believe either is the case with the definition of veganism. It is not common-sensical to avoid products with trace elements of animal ingredients for example.

Thanks for the comment. I suspect there are a couple of distinct elements that have been conflated in your arguments that I will try to disentangle. 

As far as practical considerations in the context of personal changes to limit harm towards animals go, I not only agree with you that first-order veganism is sensible, it is also one of the key reasons why I am a 99% first-order vegan. Forget animals, I am just being kind to myself and eliminating decision fatigue by following a simple rule that says : animal products, no go.  It just makes things so much more convenient and I would certainly recommend that to others too.

However, practical strategies, mental tricks and hacks should not be mistaken for ethical principles. I am sure you will agree that the  latter requires reasoning and justification not subjected to the whims of mental hacks.  If the community reifies those practical steps as a core component of the ethical baseline to be considered an adequate supporter/defender of animal welfare,  then it is clearly drifting away from the primary considerations that brought it together in the first place.

Thanks for the response. You've summarised the post very well except that, more than limiting intellectual freedom, the convention definition leads to excessive focus on purity at the first-order at the expense of broad utilitarian considerations (think of all the vitriol that vegans throw at deserters which is so irrational). 

As for your view that without the solidarity, the veganism would not be what it is today, I am not entirely convinced. To be clear, the community of interest in this discussion is the animal advocacy one and not vegans per se (notwithstanding  the fact the two of them intersect almost completely). Here are some counter-arguments to consider:

1. Animal advocates are likely to be first-order vegans or very close to it anyway. If one voluntarily chooses to make lifestyle changes based on concern for animal suffering, then one is likely to go to significant lengths to avoid animal products.  Not everyone may go  the same distance but that's okay (or so I think).  
2. Peter Singer the philosopher who arguably has the greatest claim to influencing people on animal rights and liberation is not a strict vegan and in fact describes himself as being "flexible". Yuval Harari is another person who is passionate about ending industrial agriculture of animals but describes himself as "vegan-ish". If important thinkers who undoubtedly have a great influence on people refrain from using the word "vegan", then why do you  think that as a community animal advocates should not shed that label or loosen its definition?
3. Conversely, taking vegan purity to the extreme, we have people like Gary Francione who are so opposed to any welfarist progress (regardless of its consequential value) and who insist that we should avoid meat alternatives because that normalizes the idea of consuming animals. I hope we can agree that that position is counterproductive.
4. I may be extrapolating from personal experience but first-order veganism being as clearly defined (very arbitrary but very well-defined) gives adherents the sense that they are doing enough already and dilutes thinking along utilitarian lines (what if a vegan purist compares herself to someone who is 95% plant-based but convinces 3 people every month to reduce animal products by 50%).  
5. While on the one hand, vegans could be admired for being very committed to the cause, and inspire others to do the same, they may seen too distant  which could work against people making changes that they otherwise may have been open to. Again, this is speculative and in general I think it cuts both ways. 

You may be slightly mistaken about what I am stating: the ambiguity is in the official definition even if it a sensible sounding one whereas the conventional definition is well-defined ('no first-order consumption') but arbitrary. The problem arises not so much from arbitrariness in and of itself, but rather demanding strict adherence to (and unwarranted focus on) something that isn't well-justified to begin with.  That leads to all sorts of contradictions.

On the second point, I agree that the distinctions between the two examples are somewhat arbitrary. One may argue that perhaps animal-testing in many instances is unnecessary (turns out several are based on methods and assumptions that have been around for a century and have persisted more out of inertia despite no clear evaluation of their effectiveness) but conventional agriculture depends on pesticides but I wouldn't find that argument very convincing. 

I am NOT disputing the harm to animals from eating or consuming animal products in any-way nor do I believe that the harm itself in some sense vague or poorly defined (on the contrary, there are very few things that stand out as clearly as that).

 The distinction I am trying to draw is between first-order or direct harm from a given action and the multiple indirect - second-order and beyond - ways in which that action can lead to suffering. In the conventional definition of veganism, the focus is almost entirely on the first-order effects especially when it relates to personal identification with the term "vegan". This asymmetric focus happens at the expense of consequentialist considerations of our actions. 

Not sure I follow this but doesn't the very notion of stochastic dominance arise only when we have two distinct probability distributions? In this scenario the distribution of the outcomes is held fixed but the net expected utility is determined by weighing the outcomes based on other critera (such as risk aversion or aversion to no-difference).

Not sure I agree. Brian Tomasik's post is less a general argument against the approach of EV maximization but more a demonstration of its misapplication in a context where expectation is computed across two distinct distributions of utility functions. As an aside, I also don't see the relation between the primary argument being made there and the two-envelopes problem because the latter can be resolved by identifying a very clear mathematical flaw in the claim (that switching is better).   

This is a very interesting study and analysis.

I was wondering what its implication would be for an area like animal rights/welfare where the baseline support is likely to be considerably lower than that of climate change. 

 If we assume that the polarization effect of radical activism holds true across other issues as well, then the fraction of people who become less supportive may be higher than those who have been persuaded to become more concerned  (for the simple reason that to start with the the odds of people supporting even the more moderate animal rights positions would be rather low) .

I reckon though that such simple extrapolation is fraught and there are other factors that will come into the picture when it comes to animal advocacy.  

This is a very interesting study and analysis!

I was wondering what its implication would be for an area like animal rights/welfare where the baseline support is likely to be considerably lower than that of climate change. 

 If we assume that the polarization effect of radical activism holds true across other issues as well, then the fraction of people who become less supportive may be higher than those who have been persuaded to become more concerned  (for the simple reason that to start with the the odds of people supporting even the more moderate animal rights positions would be rather low) .

I reckon though that such simple extrapolation is fraught and there are other factors that will come into the picture when it comes to animal advocacy.  

I didn't get the intuition behind the initial formulation:

$EU\left(f\right)=\alpha {min}_{p\in C}{E}_{p}U\left(f\right)+(1-\alpha ){max}_{p\in C}{E}_{p}U\left(f\right)$

What exactly is that supposed to represent? And what was the basis for assigning numbers to the contingency matrix in the two example cases you've considered?