I guess you haven't checked any port listings lately?
The majority of ports below 1024 (oh hell, almost every port below it, and quite a few above it) are reserved for use for specific programs. However, thats not to say you have to use those ports.

I can think of one good reason not to use ports below 1024.
Whilst the specific ports aren't secure, ports above 1024 are generally not actually used for specific purposes.
Yes, like I said in my first post, I'm aware that ports below 1024 are generally reserved for specific services. But also, just about all ports from 1024 - 5000 are also reserved and registered with IANA for specific uses also - http://www.iana.org/assignments/port-numbers. Like I said in my previous post, I'm not saying that we should change the default values 1024 and 5000, I'm just saying that users should be allowed to enter a value lower than 1024 if we really want. If the main concern is that mIRC would be involved in port conflicts, then like BoredNL said, a warning could always be issued if the user attempts to change it to a port lower than 1024.

Todd, there is really no point to posting the same thing in 3 different forums...
Sorry about that. It's just that this topic is moving further and further down, and posting a reply doesn't bump it up to the top. I also haven't really seen any official replies such as from Khaled or any mods, and it looks like this issue is getting hopeless.