To me this is VERY unsightly and I have the option in setting set to hide artists who only appear in compilations but i get the same result no matter what, including using different scrapers to scrape the info:
Almost always due to incorrect tags. Check your tags in something such as foobar2000.
Always read the XBMC online-manual, FAQ and search the forum before posting.
Do not e-mail XBMC-Team members directly asking for support. Read/follow the forum rules.
For troubleshooting and bug reporting please make sure you read this first.