I think we should allow them but carefully watch the answer quality. It can be really hard to find out best practices in niche programming fields like computer graphics, especially because the vastly different paradigms of GPU programming mean that the established patterns from "normal" programming can't always be applied. This being a community of computer graphics experts, we should be in a perfect position to collect actual best practices for computer graphics. I think this potential should not be easily dismissed, just because "answers might be opinionated".
Instead, let's try to be careful with answers and make sure we encourage the same high quality for these than for any others. So what makes a good answer to a best-practice question:
- Don't just answer with "here's what I do, it's the best!"
- Do include objective pros and cons of the practices your answer covers.
- Do include authoritative references which show that it's actually established practice where applicable (i.e. when your answer is more about "the accepted practice" than "the best practice", which can also be an important consideration).
- Do point out if certain choices are merely a matter of preference (and list the available options).
If we take care that answers to these questions don't deteriorate from our normal standards, I don't see any harm in having these questions.
After all, any programming question probably has multiple solutions which could invite answers fighting for which solution (i.e. practice) is the best in the given situation. Asking for a practice explicitly doesn't really change that.