For posting:
- invitations to games (you can also use the New Game menu)
- information about upcoming tournaments
- discussion of games (please limit this to completed games or discussion on how a game has arrived at a certain position ... speculation on who has an advantage or the benefits of potential moves is not permitted)
- links to interesting related sites (non-promotional)
Yes, it is promoted. And it is hidden in this line of the rules:
The rules are the same as for normal chess with these differences: [and the list of extra horde chess features]
:-)