I might tell you that I also have the same problem replying to the comments that people do manage to leave! What I find though - which may or may not be unique to my browser / PC - is that it is invariably only swallows the comment the first time I try to leave it. It tends to publishes on the second attempt.
The tips would therefore be (if you can face that extra step):
a) Copy the comment to your clipboard before hitting 'Post'
b) Try a second time (but if that fails, by all means give it up as a bad job ;) )
Next (normal!) post coming up soon...