I made a store on top of someones store because I thought the dude was just shopping, but he was threatening me that he was going to get a gm. His store is ontop of mine anyway so it cant be a big deal right?
Unless you glitch abused to get a store opened on his spot, the worst that could happen is that your merchant gets closed by a GM. This is assuming that he started setting up his store before you, and not after you.