|User 1||User 2||User 3|
|User 1||Mr Blue||Mr Red|
|User 2||Mr Green||Mr Orange|
|User 3||Mr Yellow||Mr Purple|
In the above example, when User 1 sees posts on the online forum that are made by User 2, he/she sees them as coming from Mr Green, but when User 3 sees the same posts he/she sees them coming from Mr Orange. Likewise, when User 1 replies to User 2's posts, User 2 sees that response as coming from Mr Blue.
On all posts, the users would be able to reference the target user names as an object embedded in the text of the response. This would then be changed when viewed by other users. So in the above example, when User 1 responds to User 2, he/she might say "I agree with
When a user first joins the online service they would begin interacting in the public spaces (e.g. forums, Q&A, blogs, micro-blogs etc), but having got to know other users in the public spaces, the user would be able to add the other users as friends (social network functionality) or send private messages (email functionality). It is worth noting that the public spaces would not be open to the internet - the user would need to have an account (similar to existing social media services).
There is a risk that anonymity would deteriorate if users didn't refer to other users by the embedded object method, or if other uniquely identifying information is provided (e.g. photos) (or potentially via stylometry / writeprint). Obviously there would also be a risk in the event the servers are compromised.