But you forgot a vast amount of TV rips and open source programmes that are available on IRC and free to share. Because I am living in a non-english country, I often download TV series rips, because I don't like dubbed versions

Well for a start I never said that, your quoting someone else. However I wouldnt doubt that if u actually checked on it you would find TVrips are illegal as most TV programs are copyright meaning you do have to get permission to reproduce them, i very much doubt that any irc channel is doing this. (personally I dont care about tvrips one way or the other, but lets be real about it, tvrips well be illegal in 99% of the cases)

As to xdcc using md5 hashed crc values, it would be the simplest of things to just add the md5 crc value to the filename, and thus 2 files like named files would NEVER match as they would have the md5 attached to the filename, beyond that I dont know just where you think your gonna put that md5 of a partly downloaded file, I doubt that you want to start messing with secondary data streams as not all OS support them.