I'd like to see all the replies that have been made to the comments that I've posted on Wikipedia talk pages. Is it possible to do this (without manually adding each of the pages to my watchlist?)
As far as I know, this is not possible. That's because MediaWiki doesn't actually know what a reply is or that sections on talk pages have some special meaning.
I guess you could write a program that checks all the talk pages you wrote to for replies, but I don't know about anything like that that already exists.
Also, LiquidThreads should solve this (and other problems with Wikipedia talk pages), but I don't think it will be finished any time soon.