Gnus provides fuzzy matching of Subject lines when doing
things like scoring, thread gathering and thread comparison.
As opposed to regular expression matching, fuzzy matching is very fuzzy. It’s so fuzzy that there’s not even a definition of what fuzziness means, and the implementation has changed over time.
Basically, it tries to remove all noise from lines before comparing. ‘Re: ’, parenthetical remarks, white space, and so on, are filtered out of the strings before comparing the results. This often leads to adequate results—even when faced with strings generated by text manglers masquerading as newsreaders.