Not all fall in to definition 3. I think you can pick some anons by the way they write, the phrases they use, the number of points they always include in lists, etc.
As long as the name "Anonymous" is at the top of the post there is plausible deniability for the poster, that it might not be them posting but some anon with the same style, or mimicking their style, so it can't always be taken for granite.
A little flavor doesn't hurt, and if they think it's all about them then that probably just puts them in a certain age group. I don't worry about it; scroll by or engage, it's really up to the individual.
At the end of the day we're not anonymous at all to certain groups of people, so the anonymity is more of a layer of protection than an impenetrable shield.