So a few days before we received the answer, we in staff-chat realized another possibility of who this mystery ban evader could be: kaan55.
Back in 2018, kaan55 harassed two women from TASVideos through discord pms: GoddessMaria and myself:

I specifically told him off at the time to not compliment me more than he knows me whereas with Maria, that was her only response to him. In 2020 he sent me more creepy messages.
A little while later, while talking with Maria, we found out that we were both harassed by the same user. Furious, I brought it up to staff-chat and went to confront kaan in discord dms. I also posted this on my personal twitter as #metoo was a big thing at the time and I wanted other speedrun communities he was in to be safe from him. kaan made a bunch of excuses and explained that we were the only two women on tasvideos he harassed as after all...

I requested him to publicly apologize in the tasvideos discord, which he did, but we did not ban him at that time. He then deleted his messages to me and Maria. Meanwhile Spikestuff reached out to the Crash Bandicoot community since they happened to be involved there already, and found out that kaan harassed people there too. The Crash community on the other hand, elected to ban him outright.
Instead of seeking to improve himself as I hoped, over the next year kaan tried to target spikestuff for their interactions with the Crash community and went to Noxxa to try to get them removed from staff, which spike was at that time.
We decided enough was enough and elected to ban kaan55 from TASVideos.
There were later sporadic appearances of him on the tasbot discord server where he complained about his ban on tasvideos in various ways, including trying to manipulate dwangoAC by criticizing his ability to moderate in 2023. Additionally he badmouthed tasvideos in this Classic Sonic Series RTA discord where a moderator reached out to me for info. The Classic Sonic Series RTA discord banned him. He simply left the TASBot discord.
2 years later, an account named AnonymousReaper surfaced in the apology and mission statement thread, making vague complaints about tasvideos and some prominent members such as, Spikestuff, Samsara, and myself. We initially thought this user was OtakuTAS, but we later realized that it could be kaan55. He then revealed this to us on December 16:

As Samsara was now preoccupied with personal matters, I took over and responded myself:

In full defense of the response I gave, I completely forgot just how manipulative kaan55 had gotten. I didn't realize just how completely and utterly delusional he had gotten and might in fact be beyond saving. I truly would have forgiven him if he had given tasvideos an earnest apology INSTEAD of doing the weird reaper stuff.

This reply of his is so extremely manipulative. It legit kinda hurts my faith in humanity a tad. He never exactly said what his screwups were. He continued to tell me how we should handle him, even though that's not remotely how bans work.
I was suffering from some bad sleep so I didn't respond that day, resulting in the following message from him:

I was flabbergasted. He assumed that the reason I hadn't responded was because I was conflicted. When I received his original response, I had actually already made up my mind, but this solidified things further. kaan is sounding like an evil vizier trying to usurp power from the monarch, except he had none of the actual power to do any of it.
This man is completely and utterly delusional, and therefore will remain
permanently banned. We are hosting this evidence on the server because he is a safety concern and not to be trusted under any circumstance.