Before I respond to puterfixer's post, I have a theory on what has turned this thread into such a spat war. This suggestion is a Spell Checker, not a Spell Fixer. In my opinion, the best way that this could be implemented is if it:
  1. was able to be toggled on and off. This would have to be the case, as everyone would not want to download and install aspell with their native dictionary.
  2. could use multiple dictionaries at the same time, for people chat in both English, and Spanish for example. I am not sure if aspell supports multiple dictionaries, so maybe an option to turn aspell off for certain channels, like you can turn logging off for certain channels.
  3. did not fix your spelling automatically for you.
  4. did not popup any spelling suggestions
  5. had a way to change the formatting of a mispelled word. instead of turning it red and underlined, maybe turn it bold.
  6. had an easy way to add words to the dictionary. I would suggest actually adding it to mirc.ini as not to 'corrupt' the dictionary with mispelled words, like lol, rofl, etc.

Furthermore, I do not think it would actually take too much work to implement this. Since aspell/pspell is open source, there is many references to learn from, if need be. I know in other languages, this could be done in a matter of a few lines of code. Of course, this is just my view on it, I really have no idea since I am not familiar with C++, or the mIRC source code obviously. But since Mr. Mardam-Bey recently added the 'multi-byte' edit box, the text formatting for a mispelled word would not be a problem I do not imagine. Now to reply to puterfixer...

Writing a built-in spell checker for a communication environment based on getting the message through quickly while disregarding quality, is simply a waste of human resources.

IRC was not based on getting a message through quickly while disregarding quality. IRC, along with email, which I despise, has become a means of communication where spelling and grammar (thus quality) is, for some reason, forgotten. How annoying is it when someone sends you an email that is completely void of any punctuation, thus turning it into one long run-on sentence?

The fact that people created add-ons for mIRC to turn it into an e-mail checker or multimedia player is simply an example of the power of the scripting language. If one feels like it, he could write a mIRC script to replace the industrial computers controlling the robots in a car factory. This doesn't mean that such a feature is normal for an IRC client. Neither is e-mail checking and multimedia players, there are specialized tools for that.

Extending this application beyond its scope will only turn it into a strange piece of software, like mixing up the genes of a sheep, a shark, a parrot and a cactus just to see what could come up.

Now I'm really not sure what you were trying to get at, but I do not think adding a spell validator to a program in which is used for typing is really that far fetched.

It is silly to request users to use correct language on IRC, even that some people would very much like to see those abbreviations or nonsense gone from their screens (me included).

How you type on IRC portrays an enormous amount about yourself. The people that this wouldn't help out are the people who mispell words on purpose, but then again, there is nothing that could help them out.

However, it is stupid to force users to do so - see how much you can determine people not to use excessive colors in channels.

No one is being forced to type correctly. This would be a non-intrusive spell checker. So non-intrusive, that, from what has been suggested by myself and others, shouldn't even offer suggestions. All it does is notify you of mispelled words with some sort of text-formatting in the editbox whilst you type.

And, it is a waste of time to implement something that is not desired or needed by the majority of the users; there are other things on the "to do" list, which have more supporters than the idea of a spell checker.

I think you'd be surprised at the number of people who would think it'd be a good idea. I do not keep up to date with the "to-do" list, but I imagine the "to-do" list is filled with things to benefit scripters, not people like me who use mIRC solely to chat with.

What would happen if people found out the new version prevents them from sending messages as they did for years, or annoys them with underlined words they mistyped, or even makes chatting feel like writing a document for work?

This would in no way prevent anyone from sending messages with mispelled words. If for some reason you found you did not want mIRC to notify you of mispelled words, simply turn it off. Furthermore, people would not "just find out" as soon as they opened mIRC that it "annoys" them with mispelled words. They would have to go to and download aspell and their dictionary. This feature would not work without them.

They use IRC to chat free of any restraints, to express themselves creatively, to relax.

Not all people use IRC to relax, some actually do business with it. Some people actually use it to learn. When I join a help channel requesting help with something, php for example, I do my best to organize my thoughts, including spelling and grammar, cleanly and efficiently. People, including myself, would much rather help someone who sounds professional than someone who enters a channel and immediately starts spewing out jibberish.

Throw in a restriction which directly affects the purpose of chatting, and you've got a serious problem.

Remember, there would be a way to turn it on and off. And also if they didn't want a spellchecker, they probably wouldn't have downloaded the dictionary.

These are my thoughts on the matter, and coupled with Jundas and DekuHaze make a rather convincing argument in my opinion on why this is a good suggestion. Basically, I have come to the conclusion that, if you do not want mIRC to check your spelling, don't enable, or disable the option, or don't even download the dictionaries, and you have nothing to worry about.