A bit late - but first of all, thanks, Asen. I thought the original points were pretty good for these purposes.
I'd have two points here about the overall advice:
1) Not everyone always wants pure immersion or pure storytelling. It's pretty common to sometimes enjoy both, but want a little shift one way or the other.
2) Sometimes people enjoy in particular immersing in their storytelling. I've certainly greatly enjoyed A Thousand and One Nights - where you have a character who engages in telling stories with the other PCs.
I think the point about competence is good, but could use a bit of an example. If I'm playing a legendary expert engineer who knows every bit of his ship and how it works - then other PCs often will ask my character things like "Can we do X?" and "How long will it take to do Y?" In some games, this always results in me turning to the GM and asking the same question - which doesn't give the feel of being an expert. If I can actually give a definitive answer back, then it can help the feel of being an expert.
On the tangent of personality mechanics,
Not necessarily. Have you never had a reaction that surprised even yourself ? I know I had. Real people do not always act in the most reasonable and logical way as characters in a role playing game do. These mechanics also help with that.
I feel the same way about social mechanics. We're not really consciously in control of everything we do and decide. I've been talked into some amazingly stupid shit in the past and made really poor choices. So I can see my character doing some that are "out of my control."
Conversely - When I'm immersing in a character in an RPG, I often find that I don't act in the most reasonable and logical way - and often make choices that surprise me, just like I do in real life. By getting into character, the same surprising, unconscious decisions can happen - and they're often really interesting for having done so.
That doesn't mean personality mechanics are wrong - but they're a matter of taste, and not necessary in order to get surprising and/or illogical behavior.