Using file size also leads to false positive.
If you are going to use the hash, then there's no need to store the modified time or the file size as the hash is meant to be a way to uniquely represent the content of the file, if the hash change, so is the content of the file.
Given what was mentioned by Khaled on this, what you are talking about is certainly not a bug.
but also causes mIRC to have a false negative when the contents change without changing the timestamp.
That's not supposed to happen.
The only real improvement would be to use hashes all the time imo.
