In your game, there are probably at least 5-10 other players. They all have characters, just like you do. But what makes your character stand out? It is hard enough for you to describe your character in your own posts, even harder for the other players!
In a movie, all the characters are dressed differently, they speak with accents or dialects, the move in different ways and they are automatically seen as different characters. In a written environment, it is not as easy to distinguish between the characters. Have you not had to stop reading in the middle of a post to think about which one of the characters it is about? I know I have.
If you include small descriptions of your character, everyone will eventually be able to include your character in their own posts in ways that better explains your character.
For example, if you write in your posts that you character tilt its head to the side each time when he or she is thinking, it is a signal that this is something that is unique and identifying for your character. Next time on of your friends include your character in a situation where it thinks, they can write that too. This gives the more life to the character.
If the Game Master allows it, it can also be helpful to include such instructions in your character’s character sheet or background page. By helping others use your character in their posts, you open up for more possibilities for yourself to follow up on their posts.