It's the "humble" bit in IMHO that is annoying, because it's so clearly insincere. At least when you say something like "It seems to me" or "My personal view is..." you leave open the possibility that you actually do accept that you might be wrong.

As with "smileys", these internet acronyms are presented as a way of avoiding giving offence by making communication less likely to give rise to misunderstanding. But in fact I would suggest that they have the reverse effect, and that taking time to write what we mean is still a better way of achieving those ends.

(The solution to the problem of misunderstood irony might best be solved by the typeface Mencken once suggested, "ironics", with the letters sloping the opposite way to italics. Unfortunately it doesn't appear to be available to us.)