If a picture is worth a thousand words...


tl;dr - find what works for the game and group. Players are often too afraid to speak up and instead drop out because of things such as this.
I prefer a happy middle ground.
A post should include enough detail to explain what you are doing (if it matters) and have something for the others to interact with. Taking a seat is an action, and unless you're conveying that you're a lone wolf, or something to that effect, where you sit is not typically a pertinent piece to me or the scene (barring, of course, sitting next to someone or away because of some combat or intrigue going down). I also see nothing wrong with giving a basic hair color and length or style. A description should give me a fair picture of the character. How tall, general appearance, clothing, and any obvious weapons. (The only time it should reveal more is if that's the game's primary purpose of advertising a couple's story and you want to know what character would be a good fit). Otherwise, I agree, anything beyond appearances should be discovered through interactions.
The general accepted also differs between the styles of games. In a d20 game, I'm surprised if I get anything more than a general height, weight, eye, and hair color. Since the focus of those games is adventuring and completing missions/quests (Not typically romance or personal interactions). Whereas a guided freeform, where most of the focus is on stories surrounding a given couple or group, far more emphasis is on writing novel-like posts akin to Tolkien or your steamy romance novels.
Though to your point SunRuanEr, words hold importance and if one 'skims' there is a chance they miss something that could be important. More is not necessarily better. My ask in such situations is the important items are called out if that is the case. I've had players complain about attempting to keep up because several posts were small papers. I believe moderation and getting a feel for the group's preference is ideal. Since some players are afraid of giving offense by bringing it up, they'll just give up and leave quietly.
Your mileage may vary, but that's been my experience.