We will look into the issue of not being able to like those posts. I'm not sure what is up with that. I'll put on my coding hat in a bit and take a look.
edit: Right now we have it set so you can only Like open threads that are less than 180 days old.
Sorry for buggin' ya, but is it going to stay that way, or might you plan on changing it?
I understand there's a reason for the time limit n' all, but there's a lot of posts older than half a year which deserve thanks (IMO, anyways). Case in point would be the modifications that have been out for longer than 6 months.
What I would have liked is to get notifications when someone likes your post. Please see if its possible to do that.
I dunno about Notifications, but if you look in your profile, you can see the latest likes you received. (Sorry if you already knew about that feature; if not, now you do. :>)