So apparently, if I browse LFSWorld.net when not logged in and choose to display LFS-teams (= I'm viewing LFS Teams search-tab in LFS Racers database), the link for removing myself from the team is visible. However, it is only visible on those teams, that don't have any members at all.

In this case however, clicking that link doesn't seem to do much of anything.

Attached a screenshot about this.

It's probably how guest mode works: Essentially, you're logged in, but your username is treated as null (no characters at all). Since those teams have no members, LFS World thinks you're on all of those, since there's nothing written on the Members line, and your username is treated as nothing.