IMO the argument that we are making society stupider by introducing spell check is nothing more than anecdotal evidence and conjecture. I don't think it's mIRC's job to make opinionated calls on how people should or shouldn't use their computers. Telling people they get dumber by using spell check is not really helpful.
The real issue, in my opinion, is that to implement spellchecking in mIRC, Khaled would likely have to put in a disproportionate amount of effort for the return. The amount of false positives you get from a spell checker over a medium like IRC is likely ridiculously high. False positives are a big problem because they make users ignore feedback-- ie., your red underline would be meaningless if it popped up on every 2nd word. That's likely what would happen over IRC. How do you spell check a sentence like "u r gr8"? Those aren't "misspellings". How do you deal with the fact that many of the spelling errors would just be channel or nicknames, or shorthand notation for the various things people talk about over IRC?
I should also point out that I've used free spelling libraries like hunspell (an aspell-like library) in the past, and they are not very impressive. They tend to lack concepts of pluralization and verb tenses, so if mIRC were to add standard IRC jargon like "lol", "brb", etc., it would not handle all of the other possible permutations of these words: lols, loling, lol'd, etc... it's also important to realize that many spelling errors do not produce incorrect words, but rather, another valid word (known as a typo). Misspelling pig as pic, for instance, would not generate an error line, so this would be a false negative. With the possibility for so much misjudgment on the part of the spell checker, I'm pretty skeptical about adding this functionality.
As a final point, I think this image is useful to share, given the subject matter. The following is what my browser, Chrome, thinks of my spelling abilities. Chrome uses aspell, I think, which is what has been suggested for mIRC. Although I made no actual spelling errors in my post, Chrome seems to think there are plenty. FYI it doesn't even recognize "spellcheck" as a valid word:
That's that we'd be expecting to see, if mIRC implemented the same functionality. Except it would be worse-- I'm not nearly as formal about my spelling/grammar on IRC. I suspect other people have similar habits.
