Note: in your question, you say that "[users] vehemently oppose mentions of other distros". I have taken that wording to be disingenuous, and answered as if you meant that users oppose leaving open questions in which the OP states that they are using another distro, because I think that is what you meant (and I am one of those users), and because merely mentioning another distro has never been an acceptable reason to close, though it certainly does trigger incorrect close voting at times.
Note: in your question, you say that "[users] vehemently oppose mentions of other distros". I have taken that wording to be disingenuous, and answered as if you meant that users oppose leaving open questions in which the OP states that they are using another distro, because I think that is what you meant (and I am one of those users), and because merely mentioning another distro has never been an acceptable reason to close, though it certainly does trigger incorrect close voting at times. Note regarding Fear #2: Only high rep users can do this
If that were true, it would not be worrying. If you are proposing (which was not clear to me) that people should edit distro information out of posts on the basis of whether or not they think the question is distro-agnostic, an action I consider to be wrong, then obviously the fact that literally anyone can suggest an edit to any unlocked post is what makes it disturbing that such an action is being advocated. In chat, I said
[L]etting things slide where there's a preexisting answer to save, ok, maybe I can live with it. But people with diamonds like @Seth and @terdon publically saying things like "yeah you can edit out the distro information if you know it's a distro-agnostic issue"... this is virtually policy-making. A bunch of high rep users might just take it upon themselves to go around doing that. And telling other users what they are doing, inevitably, and everyone will copy them.
It's the "everyone will copy them" part, that really concerns me.
Personal note:
There are persistent fears within community, which often are on the verge of emotional investment rather than practical and professional view on the issue.
My investment in Ask Ubuntu is absolutely emotional and not professional. I care deeply about the site and nobody is paying me to contribute to it, though I do get a lot out of it in validation feels, friendly chats etc.