Unfortunate that one can't give a reason, really. Personally, I sometimes report people who are AFK for the entire game (I do often wait a second at the start for lag to settle and to be sure I have an opponent at the controller), those who SD twice without playing at all multiple matches in a row, who only roll or otherwise run without attacking at all... or who are annoying with taunts, to be honest. By all means, taunt that falcon punch you edgeguard with in midair, but taunting a KO punch in a lagspike when you're down a stock and 100%? Or who taunt lag-based SDs, for that matter... None are any 'always' thing, but disrespectful play in general's a great way to get an occasional report-- though I'm much more likely to simply block if their main grievance is 'being annoying'.
I'll certainly admit to one or two reports being entirely the result of rage at an unplayable amount of lag or some truly stupid tactic (rolling Samuses if I happen to lack a quick roll punish is the only that comes to mind), I honestly can't say I've used it even a dozen times in the few hundred 'For Glory' games I've played. Though, I don't understand the point of it even existing in 'For Fun'-- if you didn't want item-y stage-decided chaos, you're in the wrong mode. Also, if someone's sufficiently behind, they get a free smash ball if items are on-- that's a known mechanic rather than any cheating.
That said, I've certainly blocked people before for no greater offense than 'only used a single move no matter how many games in a row I punished it in exactly the same way...' That just gets to be dreadfully boring, and I don't see a point to playing with someone who can neither help me improve nor make for a fun match.
Though, I will admit to panic-reporting the first Little Mac who pulled of the Nair gimp before I knew it was a thing-- though I've never been so unlucky as to encounter the ZSS infinite as Robin.
