When you refresh an album from the UI, the folksonomy tags counts are not cleared from the data structures. Instead, the counts are just added again. (see mbxml.add_[user_]folksonomy_tags and dataobj.add_folksonomy_tag
This leads to strange behaviour when changing the "user tags only" setting in config, as the "non-user" tags are never cleared. You need to restart Picard to make it behave correctly after changing this setting.
It also behaves strangely (from a user perspective) if you tag something on the website and then refresh the album in Picard, since you might expect the top rated tag to change, but it may not.
There needs to be a way to clear the counts for folksonomy tags from tracks and albums when a release is refreshed.