I normally say to people that have problems with these design issues to either live with them or move on to something else.
Not something that I really like doing though.

Maybe it's time that a new scripting engine was introduced to mIRC, such as TCL or similar.
I've no idea how easy or difficult this would be to implement into mIRC and I've no idea about the license that a language such as TCL is covered by. I'm sure there is at least one scripting langauge that would be suitable license and implementation wise.

Mirc could differentiate between the two scripting languages with the file suffix.

This might please the people who get upset because the following code does not evaluate the way they might think:

if (1 && 1 || 1 && 0) { echo -a Shouldn't this be true? }

But since the mirc scripting language has no standard that says && has a higher precedence than || it's impossible to say if it's wrong or not.

Yet it would be simple to fix with some parenthesis.

if (!1) { echo -a Why? }

I'd guess strings having to have quotes would make it easier to fix things like the above line too. Where “!1” is probably taken as a string.

Perhaps having two scripting languages would make it a bit more difficult for people in help channels and may divide the community a little.
But I think it's a good idea to help to keep users who notice these things that are not quite right yet.