That's the best idea yet. If there are no responses (and no 'readmore' tags?), give an "Offer your reply" link (or "Post a response" or whatever the standardized wording ends up being). If there are replies, give a "Read more/Contribute" link (that just duplicates the functionality of clicking on the thread title, which is good because the result of clicking on the title is a common convention but isn't actually described for those unfamiliar with the convention).

Actually, replace "Offer your reply" with either a pair of links, "Read more | Post response", or a single link, "Read more / Contribute".