Hello. As someone who played and followed Yandere Simulator's development. (although not a supporter of indexing it in this wiki)
The 1980s mode of the Game established a proper canon story for the Parent of The Main Character, which is unlike The Main character, where we have more creative freedom to just befriend people. The Parent otherwise has a different backstory that is basically confirmed
In the Canon of the story.
Aishi Ryoba is a killer.
confirmed by the Tapes. Even resulting in a trial, which she basically got cleared of
Kidnaps her senpai and forces him to live with her until they become a family. (All this happened while she was a student). And there are a lot of lore hints that something similar will happen to Senpai in the conclusion of the Main game if the game actually finishes development
Do note that the 1980s mode elimination method follows the same mechanics for the main game, which include needing to dispose of the body with a lot of horrendous methods. There is a befriend mode, but there are things that you have no option but to do so otherwise, such as the death of Sumire Saitozaki, which happened before the game started
Although my general opinion is that
1980s mode is an optional content, but it is still part of the backstory of the Main Game. Although you can basically do the Suitor or the befriend method for all the Rivals. The ending is pretty much set in stone.
Not to mention, there is like a really unnecessary side content where if you fail and reach a game over, you can "SNAP". I'm not sure why this is necessary, but likely the developer wanted to portray the character as similar to how Anime Yandere are.
With all that said. I still don't believe it intends to promote such things or violence.
As the Developer himself posted a video explaining that it is at players decision whether the game will become dark or remain a cutesy dating sim-like game. Much like most simulator games, the player simply has freedom how they want the simulation to go
So I believe it should still remain in the wiki. And doesn't really promote nor endorses such action the same way GTA doesn't endorse shooting people randomly.
Although I cannot defend the fixed ending. So I guess that one requires a decision