This whole ordeal seems a little blow out of proportion.
Welcome to BL. People are going to save your build if they want - whether you like it or not. Thankfully, Badspot doesn't seem to give two stuffs about nit-picking the game to death with rules that protect against build plagiarism. It is plagiarism, but the entire community already knows that you built the original to begin with. Yes, everyone has seen your gallery posting about Isar. Don't worry, no one actually thinks Valid built it. Not even he thinks that, seeing as how he admitted he was trolling you.
In the long run, you should be flattered. Flattered that someone thought your build was good enough to save and pass off as their own. Will banning one player really bring you retribution? Probably not, seeing as how the save is now out there and floating around. You really bring more negative attention to yourself by posting threads like these than Valid could do impersonating you.
Lastly, if you're so worried about your reputation among the forums, it probably isn't too wise to call the community stupid when hunting down Valid in a server. Just sayin.