Are friend-removals bidirectional?
When I remove a friend from my friend list in steam, am I also removed from his friend list or can he still see when I come online, enter a game and so on?
Solution 1:
If you remove a friend you will also be removed from their list:
Steam friend removal discussion
You can block someone and you will then appear 'Offline' to them at all times (they then cannot post on your profile either)