Suit jacket etiquette?

I'd keep mine on. Wear a lighter weight suit.

+1 keep it on

Is there a social situation where you're supposed to actually take your jacket off? I wasn't aware that there was.

Royal Navy mess diners - after port and coffee, the gathering usually devolves to a scratch game of touch rugby using the most junior officer's rolled-up jacket as the 'ball'. Other participants are permitted to remove their own jackets and play on shirt sleeves.

Keep your jacket on. If you get warm, keep it on. If every other yahoo in the place takes his off and puts it on the back of his chair ... keep it on.

While the status of the HVAC can make this difficult, you are supposed to keep it on, comfort not withstanding.

No to both. Keep the jacket on.

I think in the car is ok to remove it, as is in the shower.

Negative. You are supposed to leave it on until you get home at the end of the evening.

Dude. There are no "rules." No one is going to castrate you for taking it off (not even us). If you want to take off, go ahead. Perhaps the preference is to keep it on the whole night by "people in the know." I personally like the look of having the jacket, and don't like the tie without jacket look (looks high school to me). But if I were dancing, and I got hot, I might take it off, weighing the fact that I rather have people see me sweating in my shirt rather than me sweating profusely in my $1000 jacket.

Here's a tip, if you're concerned about doing the "right thing" style wise. Look around what other dudes are doing, and do the exact opposite, and you'll be just fine.

I keep my jacket on, unless I'm dancing. The unfortunate truth is that most jackets are tailored for men having their arms down, and bunch up terribly when dancing in frame. In that case I think it's better to take the jacket off.

+1