Im inclined to believe that there were death-threats. I dont agree with what this person did here, but it should be considered that there is a certain segment of the population that has sufficiently poor consideration for others or emotional regulation that they will send death threats to people that make them angry, and, importantly, while this segment may be more or less common in some groups, that tendency in itself does not force a person to hold or not hold a given view (even ideologies or ethical systems that condemn death threats, because plenty of people out there are hypocritical). As such, these people can be expected to exist in any sufficiently large group, to include whatever groups you, I, or anyone else consider to be an "in-group". The tesseract dev got a lot of people mad, so, it would honestly surprise me if they didnt get a few such threats just given the sheer number of chances for one of the angry people to be of the sort to send them. If anything, Id expect a shittier person to be slightly more likely to get them just because people like that tend to do more things that make people mad at them, though this should not be taken as saying that people that get death threats are necessarily shitty people or that they're deserved.

That stuff aside, Ive had mixed feelings about this whole affair. I do agree that the hidden blacklist thing was way out of line, but I find that most of the criticism Ive seen doesnt really give the right reason (in my point of view) for why it was out of line. (Namely, Ive seen a lot of it framed as "this is censorship, its wrong to make software that intentionally does not display posts from specific people/places". I dont think I really like this argument, because I think a lot of the people making it havent really considered the implications of it thoroughly. Its generally considered acceptable for users to block other users for example, for moderators to ban users from a community, and for instances to defederate from other instances if they feel the need, and these things also prevent one seeing the posts of affected users, they just happen at a different layer than tesseract did. It is censorship, yes, but one cant expect to be entitled to the attention of others, theres simply too many people that have things to say, even important things, for it to be otherwise, nobody can possibly pay attention to everyone, nor is it healthy to try, so there must be systems in place that allow one to ignore those one doesnt want to see in favor of those one does.

The problem in my view is one of consent: if tesseract had made it known upfront that using it without disabling some default setting also opted the user into its developer's personal blocklist, then, well, it wouldnt be much different than when people on microblog platforms share blocklists with others, or when people choose an instance based on that instance's federation decisions. I would not personally have wanted to use it, as I have different ideas of what I want to block and not block, but I dont think that in theory it would have been unethical for it to exist in that state. However, while the dev themself seems to have thought that they had done enough to make this feature known, based on one of their responses to the controversy at least, they clearly did not, else the public response to the list's exposure would not have been outrage so much as "well yeah, thats what that program does, dont use it".

Part of this I think is that while moderation decisions are expected of an instance, they dont tend to be expected from alternate UI software, so, what would have qualified as "making it known upfront" would necessarily have to have been been very blatant. As it was, they certainly didnt meet that bar, and it was very plausible for a new user to find tesseract and end up using this guy's list without knowing about it. This isnt something Ive seen come up in the angry response nearly as often as just "he's blacklisted people that I dont think ought to have been, doesnt he know blocking people is bad, what an authoritarian!". Though of course, I havent seen every post about this whole deal so its possible that I simply have missed that criticism and just seen the angry memes.)

While Ill agree that self-reflection in their part would have been the most desirable outcome, I dont think it was ever really a realistic one. I doubt that any but a small fraction of the population would really be capable of anything but defensiveness when they have managed to anger thousands of strangers into yelling at them, its not a situation that humans are really well adapted for or handle well, given that the conditions we arose in would not have allowed for it nearly as easily as those of today do. As such, I think that just leaving in frustration, while not a satisfying resolution or a perfect one, is probably the best ending that could reasonably hoped for here. The other likely outcome would have been doubling down further and keeping the anger going, and by leaving there's at least a chance that they might reflect on what happened once emotions have a chance to die down.