I would have to say the reason I think it's better to store values in the Registry is because it's a place where many average users don't mess around with, therefore, a user will not accidently mess with the values of a script. With an INI file, a user can just make a simple edit, and that can seriously break a script. And it's a more professional practice to store values in the Registry.
Yes you are right, less users look there, which is why it is always the perfect place to hide a virus, why give mIRC the easy ability to do that?
If you still think Registry support is useless, then why did DragonZap write a dll to do this? Just because you have no use for it, that doesn't mean the rest of the mIRC users feel the same way. I don't have use for mIRC's Agent support, but do you see me complaining about it? No.
Well I never said registry support is useless, I asked you to provide a reason why it isn't, which you have still failed to do. And as for Agent support, it serves a very important purpose. Perhaps you don't know but there are several blind people that use IRC, MS Agent support allows them to use mIRC to chat because although they can not see what is said in the channel, they can now hear it. Allowing the blind to use IRC certainly supercedes any possible reason you can give for needing registry access.