:How did it happen: I use some templates to auto-generate messages to new users. It's very useful and saves a lot of time (see  if you're curious). For a while, I and a few other users were adding {{User:Feco/XXXX}} to pages as appopriate. This would load my template into their talk page on every page view. Cliking EDIT on their talk page would throw the editor back into my template. The problem is fixed by adding {{subst:User:Feco/XXXX}} to user pages. The subst function drops a static copy of my template into the edit window, rather than forcing a template-load each time the page is viewed.