What's with the black dots?

[The Magic Jackal]

What's with the black dots? This may be in a post somewhere else, but i haven't come across it. On some envelopes there are black dots, and I can't post on them. They're not closed, because closed threads have a lock next to the envelope. So does anyone know what's going on?

 

[Ed Sullivan]

Any thread you have a post in gets a black dot.