(Voted back up towards 0.)

1. Standing up straight is low-status, because you're obviously doing it to make an impression on others -- there's no first-order benefit to yourself.

False. Slouching is a submissive gesture. It is signalling that you are not making a challenge to the more dominant members. Standing up straight but in a relaxed way is higher status. A strong core, head naturally raised, with gender specific variations. Remainder of the body should not be rigid but convey a balance of comfort and control. Gender specific variations tend to emphasize sexual organs in an offhand manner (where the low status signal is the reverse.)

1. Saying what's on your mind is high-status, because you're doing something pleasurable. This signal is most reliable when what you say doesn't have any intellectual merit.

Agree up to the comma. (The rest varies with context.)

1. Making an effort to have a pleasant conversation is low-status. It's high-status to talk about what you care about.

Yes.

1. Wearing the most comfortable possible clothes is high-status, because you're clearly benefiting yourself. (Dressing in fashionable clothes is also high-status, through a different inferential pathway.)

I don't agree with this one. Of the things people care about enough to signal through clothes, comfort tends to be low.

1. Apologizing is low-status because you're obviously not doing it for yourself.

I don't think adding 'because you're obviously not doing it for yourself' aids in understanding the apologizing status-dynamic much...

1. Blowing your nose is high-status because it's pleasurable and shows that you aren't affected enough by others to stop.

You find that pleasurable? (Agree with the 'affected enough' part.)

1. Asking for permission is low-status. Compare: recognizing that proceeding would be pleasurable, and believing that you are immune to any negative consequences.

Pleasure is a distraction again. Just say 'want'.

1. Showing off is low-status, because it reveals that the prospect of impressing your peers drives you to do things which aren't first-order selfish. (Of course, the thing you are showing off might legitimately signal status.)

More or less.