See http://musicbrainz.org/edit/16037203
I know there is something that "corrects" join phrases, if only because it keeps annoying me when I want to add Estonian stuff. So could we add an option for " Feat. " (and maybe "Feat." and "feat." if they're not touched) to be auto-corrected to " feat. "? That one is standardised via guideline so it shouldn't be a problem.