The conundrum is this. Can we come up with a mechanism that allows users to tell the author they found the OP interesting and simultaneously bumps the post, but which is not as intrusive on general readability as quoting the whole thing and adding "This".
Does a quick one-line comment saying "Really enjoyed that, thanks for posting" really disrupt the flow of debate? Should we be encouraging them rather than discouraging?
For me its not disrupting the debate, its adding pages and pages of posts that add nothing, especially if the whole post is requoted. So instead of a round the table of 4 pages, it becomes 20 odd pages which is more difficult to read (esp at work!!).
Couldn't the "like" button also move the thread back to the top of the page, in the same way that posting "this" does?
Also as I mentioned earlier, the post doesn't have to have "liked by 234 people" next to it, it could just be shaded a diffferent colour to stand out. Result would be a reduction in size of thread to a manageable level and the ability for quality posts to stand out.
I would suggest this option for all posts, as it is often the posts after the initial OP that are the real crackers.