I went to that page, added a 'american' tag (which displays in the top tags) and then refreshed the page and removed it. I did not see undefined anywhere. If you can still reproduce this bug, please reopen this ticket.

I just reproduced this, rather simply. Using Chrome on Ubuntu, I simply opened Victor Young's page. I had no tag set for him, so I added a 'american' tag, just as you did. "more" immediately turned into an unlinked "undefined". (See screenshot).

I then removed my 'american' tag, and refreshed.

I then was able to trigger "undefined" again four more ways.

I tagged him with 'production music', which is one of the largest tags. I got a brief flash of 'undefined', then that text changed to 'production music' - it looks like the element is being given text after it is inserted, rather than beforehand. This second one's not too bad, because it's quickly fixed by the script, but the flash of undefined doesn't look good.

I then refreshed, and was again able to trigger 'undefined' in the specific way described by the ticket text above - I simply removed my 'production music' tag, and clicked 'tag'. 'More' immediately became 'undefined', and stayed that way.

Then I tried one more thing. With it showing 'undefined', and the tag box empty, I clicked 'tag' again repeatedly. Each time it would alternate what text I got - 'more' or 'undefined', switching between them.

Figuring that maybe this was a temporary situation caused by having removed the tag within the same page instance, I refreshed again. The tag box was empty. The text showed "more". I again clicked on "tag" with nothing in the tag box. I again get "undefined", and just like before, "tag" now simply alternates between "more" and "undefined".

So this one's definitely still in there, likely in multiple ways.

Thanks for the notes, seems that this bug does indeed still exist so this can stay open.

In review with http://codereview.musicbrainz.org/r/2243/