So (route for implementation) if a non-breaking-space HTML entity would not hurt an entry-left-intentionally-blank, then probably the easiest way to make it happen would be to have a "entry is blank. Do you really want to post with a blank entry?" and if the answer is no, go back; if the answer is yes, insert an   to the entry without the user having to do so manually, and ... hm. "and go ahead and post" sounds like it would be irritating for people who hit the wrong button; "and let the user hit post again themselves" sounds non-intuitive for the RTE and a little annoying for HTML.