Yeah, random people online can't affect the mythos at large.

I'd think it'd be in very poor taste and most likely against Coltrane's wishes to portray Hagrid as dead just because he is.

Why not make a RIP Robbie post? Why make a RIP Hagrid post, when Hagrid hasn't been affected in any way, as, as you say, he's a fictional character.

But since people associate him with Hagrid and nothing else, it's what you do to get some internet points and rationalize the behaviour because you can see that my comments have been downvoted by the Reddit bandwagon, without anyone arguing the actual position.