Relative URLs in images and mentions are supposed to be converted to absolute URLs by the plugin, but there are issues with the way it’s doing it. Mention URLs are being converted to absolute URLs with javascript - this isn’t going to work for crawlers, Image URLs are being converted to absolute URLs with a regular expression! There are cases where the regular expression will fail.
Hashtag URLs are not dealt with at all.
I think the whole problem of relative URLs can be approached in a different way. I’ll try to do something with it today. Thanks for bringing this up.