tl;dr: Figuring out who's right here.
For reference and to restate/clarify, there are three things relevant to how I translate commentary on my own posts. While Blank User was doing a commentary run, several of my posts were also edited - I undid some commentary/tag changes applied consistent with how I operate translations.
1. When presented with a noun and its honorific, I would translate only the name and drop the honorific. I later learned this was wrong and started adding it on (or in places where I removed it, added it back).
2. Removed language commentary tags if the only untranslated text was "untitled", a noun or a preposition. While I still translate those at all times, it doesn't seem right to be to consider these a langauge commentary. I don't normally add these, and when Blank User was going over some of my posts, I removed them. post #8455553 isn't mixed-language commentary to me when the actual commentary is English and only the name is untranslated. For the same reason, post #8869776 (rating Q) isn't mixed when the title is "Untitled" (i.e. the absence of a title, which Danbooru's commentary fetcher renders as the word Untitled). I always translate this but never add a language commentary tag for it. Relevant: topic #28907
3. Adding already-English text to the translated section if the full text is not English. The small case in question which primarily drove this topic's creation was post #8862306 (rating Q) where the character's name was duplicated in the title section (Evelyn イヴリン). I added only the English name to the translated section because it would look silly to repeat the same text in the translated section (Evelyn Evelyn), which Blank User removed so there was no translated sections and I reverted that. Because I reverted it, Blank opted to instead duplicate the already-English text into the translated section, which I also removed. It felt like Blank was trying to force an all-or-nothing so there would be no dim-grey text, which meant either leaving the duplicated name alone or adding already-English text as "translated" commentary.
I realise I was definitely wrong on point 1 because it was already policy to retain honorifics. However, 2 and 3 make no sense to me, especially 3. I don't consider English text translated which is why I didn't feel it appropriate to duplicate that into the translated section. Blank User later sent me a DMail asking me about its removal, saying that we "need" to do it because of "accessibility".
We don't have a policy on this, so it felt to me like Blank user was trying to assert their own way of doing commentary as the way it needs to be done, with what felt like considerably flimsy justification. Using language commentary for untranslated nouns or for an actually blank field which we render with a word feels like taking language commentary tags to the extreme. Neither of us can really be proven right about the third point, it really comes down to common sense, but it's not really clear that would be. It seems like either direction could be fine - I have no real reason to remove it, and similarly asserting that we need to duplicate text to prevent greyed-out sections sounded to me like trying to treat a personal preference/accessibility pain point as policy.
It's not a big a deal as the topic or DMail exchange may make it seem. We're just mainly looking for a second opinion to settle our differences here (except for point 1, that was fully my wrong, and this wasn't highlighted in our exchange).