*.html URL alias cached but not displayed

Take a node and give it two aliases, [nid] and [nid].html. Both are cached, the first with 239.html, the latter with 239_html.html.

Visiting the first alias, anonymous users see the Boosted version after the first visualization. Visiting the latter the cache file isn't retrieved at all. Maybe some changes are needed on htaccess/boosted.txt instruction file to prevent this case with special characters and punctuation?

Second question: why if i've one node (nid = 239) there are node x aliases generated cache pages instead a single cache page for all aliases? Thanks.