wow... I'm honored guys. Quoting me 4 posts in a row, that's just wonderful.
Well... let's go ahead and start with the second post first... I did forget to change that. I don't actually main MK anymore, I main Kirby. I enjoy MK, he's my favorite character to play as, but I main Kirby. My apologies for not changing that.
Then the third one. I would, but I'm not going to.
Now for the first and third. His weight is in fact a weakness, yeah. At one point there was a thread in the MK discussion board that had a list of moves that can counter MT, and, as I remember, there were a lot of them. All of his B moves have a recovery time if they're used in the air, leaving a lot of chances for mess ups, even if they don't happen often. He doesn't have a lot of kill moves, even if he is good off of the stage. He does minimal damage with a lot of his moves... I'll think up more later, but I'll let you tear these down first, mkay?
The moves that counter tornado are often laggy(like smashes) and often aren't mobile(being ground moves), so the MK can draw in, bait the move, and then punish.
Also, the B-time recovery move is a drawback that the MK user has to overcome, not one we can exploit. An extreme example is like Olimar's ghost Pikmin glitch, which we can now replicate. Yes, all the pikmin become useless, but it won't happen unless Olimar himself choose to pull of specific inputs. MK won't choose to tornado or drill or cape in the air unless its unpunishable, and if he chooses not to, there's nothing we can do about it. His aerials certainly make up enough of a usable moveset to use in the air, the specials are just luxuries that he doesn't have to use.
He doesn't have a lot of kill moves, but those kill moves are fairly reliable. Furthermore, his kill moves are distinctly seperate from his "damaging" moves, so he won't have to stale his KO moves to put his opponents in KO range. The MK just has to not spam tornado the whole time, or use D-smash constantly.
how is the damage minimal? Tornado, fair, bair, uair, and a few others rack up damage fast.
His weight is in fact a weakness. Usmashers(and u-tilters) KO MK pretty early.
However, lots of Usmashers coincidentally have bad recoveries(Snake, Olimar, Ganondorf). So techinically, while it is a weakness, a lot of character who can exploit this also are vulnerable to MK's strengths. Nontheless, its still a weakness. Just not very easy to exploit.