mdwh: Animated emoticons are less annoying than animated avatars for a few reasons:
1. They're smaller. The biggest one, I think, is the spearman-tank one, which isn't especially annoying and isn't used very often. Most are quite small, like

. That smiley isn't as annoying (in an aesthetic sense at least

) as an avatar-sized epilepsy-inducing flashing 'PANIC', wouldn't you say?
2. We can only use emoticons that TF allows us to use, unless we can be bothered to copy them as images from other sites (and even then, because they are images, they aren't allowed in sigs). An animated avatar could be anything, unless it's pornographic or racist, for example. I'm not sure that the mods would care to enforce a ban on 'annoying avatars'.
3. As you say, the animated emoticons are within the text of the post itself. This means that it does not distract you so much from the text, as it is already inside it. The avatar is separate from the text and so is more distracting.
4. You can un-animate emoticons by pressing Esc, which means you get all the emoticons but without the animation to annoy you. In order to get rid of an annoying animated avatar, you'd have to turn avatars off, and I personally think CFC looks better with avatars on (there are a few I'd miss) although that's just personal choice. Thing is, that's the personal choice of a lot of posters.
5. Animated emoticons (for the most part, anyway) serve a purpose. For example, if we look at

again - this emoticon shows disdain in a way that use of text would be difficult to convey. (We've all had those 'sarcasm-over-the-internet' moments.) An avatar is meant as a picture which posters can recognise you by, which in some way represents your personality. What are the benefits of making it animated?
6. Some of them just plain rock.
I do, however, agree that animated emoticons in sigs are annoying, because they are not in the body of the main text. They aren't as annoying as animated avatars would be (because they're smaller) but they aren't really aesthetically pleasing, especially the various guns.

?

. (See? Disdain.) However, I wouldn't go so far as to ban them. Enforcing a ban means wasting moderator time, which could be spent
banning Perfection stopping spammers, on warning new users about their sigs - it would be pointless.
The introduction of animated avatars and the banning of animated emoticons in sigs have the same problem - needless complexity.