I am not going anywhere near changing how separators work :-) If you do not like them, you can disable them by entering an empty character in the separator box in the Options dialog. That is what it was designed for.
When I first started working on mIRC, I went through a huge amount of effort to display incoming information in a clear way. Most IRC clients at the time displayed all lines one after another and it was almost impossible to distinguish one event from another. The separator helped group different events. Unfortunately, it became an endless and almost impossible task. I had to add increasing numbers of exceptions and internal states throughout the code for different combinations of events across different networks. I am no longer doing that.
What you are seeing with these notices is really a server design issue. Server coders should never have used notices to display large amount of information to users. It shows how disconnected some server coders are from how GUI clients work. Prior to this, a notice had always been used to indicate a special message that was meant to alert a user to a particular event or important information. That is why a notice was assigned a special sound in mIRC. And why a notice is always surrounded by two separators. It had never been used to display streams of information to users and probably was never intended for that.
The worst example of this is IRCnets use of notices to send the /squery alis list * channels list. This makes it impossible to parse or display the list in a usable way without checking for english language combinations of text to determine the start and end of a list, set internal states, and so on. This method completely undermines the purpose and utility of using numerics, which make it clear to clients what a server message represents, when a group of messages start, and when they end.
