Didn't even know this had been considered... "Support" seems like a good one-word solution, but my ideal solution would be multiple modes of +1/favorite/thumbs up/whatever. My thought for a while now has been that I'd like a range of emoticon/smileys at the bottom of a post, or perhaps different words. Each of these could be clicked, allowing a range of quick expression: from sympathy, to astonishment, to sadness, to congratulations, to agreement, to just plain "read this and couldn't think of anything else to add".

I find that people (including me) who read posts on DW (and LJ) often have nothing substantive to add, so they don't. This has the effect of making it seem like no one is reading the posts, and increases the feeling that one is shouting in an empty void. Adding some quick way to express support (/sympathy/astonishment/inability to think of anything useful to add/etc.) would hopefully lessen that feeling, increase people's willingness to post (because it would feel less like words thrown into the void), and increase interaction.