I'm not completely sure about this, but it seems that comments can't exceed 1000 chars.
I managed to write a comment a little over 1000 chars, but when I tried to save it I got a server error. When I reduced it to below 1000 all was fine.
I'm not sure where the limit is, exactly, but it seems like it's close to 1000. Is this a bug, or is the database backend just setup like this, for some purpose?
The reason this is happening is due to DEFAULT_MAX_COMMENT_LENGTH being defaulted to 1000. Will need to talk to their developers for more info.