Well then, if you're gonna add italics wouldn't the next logical step be "where is double underline???" and "where is overline???" and "where is strikethrough???" "where is subscript???" "where is superscript???" I think you can see my point? mIRC is a _chat_ program, not a wordprocessor. You're right italics do have purpose in English rules, such as what Hammer mentioned. But, both APA and MLA allow you to substitute underline for italics. Why? Because not everyone has the ability to use italics. As was said, old typewriters could not handle this.
You said that "the majority of people i've mentioned it to" liked it. Well give me a number. "the majority of people" could mean 2 out of 3. Thats not that great. If it were 700 out of a 1000, well then I could say maybe it is needed. And if there are 700 people out there agreeing with you, how come there hasn't been 700 replys to this post saying "I totally agree with you, add italics"?