I think he was just wondering how that would be physically possible, but magic is a good enough explanation for this. Some swords would have pretty poor cutting ability like this one (mostly those specialized in thrusting) so it can be assumed that having this pass through ability sacrificed it's other stats for whatever reason.

I approve of the characters joining.

My spider eating suckerfish has been discovered! How very observant of you to ruin the surprise! And ironic how my grasshopper would end up eaten when she's inspired by Attack on Titan anime with her jumping ability and swords making her seem like the good guys (who actually swing around on cables rather than jump and they get eaten by titans).

For the IC posts, maybe it's a running gag that the fire user's gender is often debated like that and he gets angry, especially if they end up calling him a she. Of course he'd insist the entire time that he's a guy but they maybe don't all believe him.