I hate to say it, but I do not support Nifflas' action here.
IMO, the statement was neither a joke nor a serious flame. It was an exaggeration. There is no way that the OP honestly thinks that Saira does indeed have the worst control scheme ever in the history of platformers. Of course it's not. It's like when somebody says "it's as hot as the sun out here." Of course it's not that hot outside. It's just really hot.
That is what we call a rhetorical device in English. His words say one thing, but they mean something else. An exaggeration isn't meant to be taken at face value, because everybody knows it isn't true. A statement like "Saira has the worst control scheme ever in the history of platformers" does not mean anything beyond "there is a big flaw in Saira's controls."
I'm sorry, but I do not believe this guy is trolling. I do agree that real trolls should be banned; if there is somebody who flames you and your games without end, who will never change their opinion, and who is only here to make our lives on this forum hell - then that person deserves a ban. But in a situation like this where the person has only made one post and isn't an obvious and unmistakeable troll, you can't be quick to judge.
The way you handle negativism is important, and people really appreciate it when somebody with such a status as you is approachable. If you
can show somebody that you have a good head on your shoulders and are responsive to criticism, they'll be less judgmental of you. If you ban them... you'll make things worse.
That's just my opinion.