Alright, so - there have obviously been past questions about updating one's username, e.g. Changing user name does not update @lerts / cites?, Change all @username references in comments when a user changes their name?, and notes about making name changes public for clarity, e.g. Make the "past names" list public info for 30 days after changing your name.
The two relevant points from questions/comments like these can basically (as far as I can tell) be summarized as follows:
Editing past mentions/alerts for old usernames is probably status-bydesign due to the technical difficulty of doing so and its vague pointlessness.
Here I am to make a counterpoint/request that hopefully will not bring down too much wrath upon my head: this sucks for trans users who update their username.
I was pretty active pre-name change, and scattered around the network are tons and tons of references to what is now my deadname. Comments, chat messages, references in answers themselves, and I'm sure other places. I understand that making updates everywhere across all users any time anyone changes their username is...probably unnecessary. However.
I would like to propose that some sort of pipeline/process be implemented so that users could request that their deadname be removed from the site as best as possible. Obviously this might not be able to reach every single mention - ones in answers, for instance - but I'd like it to not be insanely easy to figure out my deadname from looking around. Edit: I completely agree that a fully reliable/completely generalized version is impossible; I'm just looking for a tool that provides at least some assistance.
Please note that I'm not asking the entire network be scoured for every single mention - I'm asking for a semi-automated process, if possible, that can be implemented upon a specific user's request that gets maybe a majority of these old mentions, and potentially some sort of policy where it's allowed to edit old answers/etc to update names.
EDIT: Have been told in the comments that comments are purely text and don't retain references to userID. If this is the case, this is an even more difficult feature request than I thought. However, I'm not going to retract it, and instead ask if there are any possibilities here. I think the underlying problem I've pointed out is major enough that this request is worth retaining, though it seems it will be more difficult/by necessity take a different form than I originally thought.
EDITED again to remove second sub-request as I misread the answer in the related question. Apologies.
Finally, just a general plea: I'm still kind of tired of Mother Meta due to everything that went down in late 2019. Please, please don't ask me 'why this is a big deal,' 'whether this is really important,' refer to me by my old username, try to figure out my old username [completely understandable if you've already run into it], or try to make this into some big 'censorship/positive commands' argument. Please. This paragraph is not intended to incite, just a beg for the overall question to be answered so I don't have to go into the weeds. Thanks.