Yeah, figured they were something wrong; seems they popped up between some places and then randomly copied the phrase that was between them. Deleting that makes everything run allright, the party switching menu works. I'd like to change some of it to my own preferences, but anyway it works like it should.
But really, the thing that happens when I'm trying to enter battle is so weird. Might have triggered it by deleting something in the script that I shouldn't have. Is there anything in there that does anything to "self.contents.draw_text(rect, @commands[index])" in the Draw Item bit of Window Command? Wouldn't see why, though, but yeah.
EDIT: Apparently, the thing is in the Commands Manager, because I tried to see if it still bugged without this script, so I deleted it, but it still did. Then I got rid of the Commands Manager and there was no error in Window_Command anymore.