> mIRC by default would not auto-accept .INI files, there was a blacklist on certain file types that would be rejected, with INIs as one of them.

Was that a reaction to the problem described in the GP? Especially in the 80s/90s, defensiveness like that was probably to solve an existing problem.

Exactly that, it was known as the ‘script.ini’ problem, the download directory was changed as well.

It would attempt to send to people as they joined a channel.

More info: http://www.irchelp.org/security/si.html

there was the funny magic string that would make half a channels modems disconnect too.

Ah, yes, I remember that. I think it was because the modems didn't differentiate between the various layers in the transport stream and took anything resembling low-level modem commands to be gospel.

This came in as a result of this. I specifically helped users fix this problem back in the day. Remember, this was the 90s.