Most of the time LFR thread are mostly trolling like this one Why does LFR drop gear?. Most of time trolling could just be replaced by posts that main goal are just to cause division/anger in the community with no real constructive point. Linking a video of asmongold and saying look at this could also be considered trolling (and mostly advertising), since its a subject that really cause people to lose their mind.
Personnaly I agree that “trolling” could be removed as a reason but I feel they keep it to give themselve a reason when some post don’t fall in one of the other categories.