I've seen multiple mentions of thedonald.win on reddit. Perhaps whichever posts you'd read that mentioned it also contained rude content?
Well to be more accurate I saw a moderator claim that any comment that mentions it gets flagged to him and even if he allows the comment, it will reappear in the moderation queue.
One mod on one subreddit? Which ones? Again, it is simply not true that this is being generally censored. That string is everywhere on reddit:
I just posted a comment saying thedonald.win on my own subreddit and sure enough it was gone.
As an experiment, I made a post saying only thedonald.win. Nothing more, nothing less. It was not visible when I logged out.
That could simply be read skew. It's also quite spammy.
Is this actually true? I see that people claim this, but I have also seen people mention thedonald.win. It does seem like reddit's spam filter catches up if people keep posting the same link over and over.