Obviously any mIRC user trusts mIRC to not contain malware. There's no reason to extend that trust to one of the few closed-source mIRC addons available. Maybe some people use it and are able to check that it doesn't do anything sinister, but the vast majority of mIRC users probably don't have the capability to check thoroughly and many wouldn't be willing to take a chance. Nor should they have to.
I'm not sure of your point on your second paragraph. Are you saying that because there's an addon available, no matter how poor or counter-intuitive it is to use, people who want this feature should just use it and not expect mIRC to add this feature? I don't really want to respond to that unless I'm sure that is what you mean, but lets just say that would be a very backwards way of looking at the world in general.
