"... Why not just explain what's in the footnote when you first mention it? ..."good point, I'll see what I can do.
"... I wonder if there's a better solution. ..."
friendfeed does the obvious thing that is it restricts view to the latest 3 by person so as to not clutter the page. Another idea I can think of would be allow you to select who you want to clamp.
"... Not an attack, just a friendly question. I've noticed you do this fairly often. ..."
to stop adding ellipses (that mess up the text especially if there is a lot of them) allowing you to read. This is especially for links or side notes that relate to the main text but is added interest. Also I use hackernews as a scribble ( http://flickr.com/photos/bootload/sets/72157600280904949/ ) for later posts on flickr
"... Bundling messages together would screw up the API and break things like twitterific ..."
No just the display, not the data itself. Just grab the latest submission. If more submissions occur in "N" minutes time frame just display the latest 3, have a click & fetch more if required. It shouldn't break app using the api doing this. Friendfeed does this well.