I'm used to use del.icio.us. There I built a button/bookmarklet which uses the currently selected text on a page as the "comment" text in the del.icio.us form.
Is it possible to prefill the comment field of the mento post form with the selected text?
Since del.icio.us just put online their new and kind of bloaty design they offer the possibility to have notes - what are corresponding to "comments" on Mento - with up to 1000 characters.
Mento still only exports the length which was possible before this del.icio.us update - that should be corrected as fast as possible. Perhaps you're already working on it, I don't know, but I hope so ;)