Some features that I'd like for sorting and saving messages in my Dreamwidth inbox:

• Automatically marking messages as 'read' once the link to the comment has been clicked on.

• Ability to create customised folders within the inbox to save certain messages containing fic comments, recs, etc.

• Indication of which messages are replies to my comments and posts, and which are part of other conversations taking place under a post I've made. I like to read these after being done with writing replies to replies.

First two are basically features of conventional email, and only the last is unique to Dreamwidth.