Why not? The goal of the coin is to show appreciation, and it's an easy way to show people who are less likely to be asshats to newcomers etc. And then we don't have to come over to this thread to check.
Special profile pic wouldn't be used too much and look like one poster on first scroll. And if it's a posters colour, some named might be getting out as a rainbow to cover all the colours they would qualify to have up there anyways