Hmmmm. This is interesting. I just recently found myself looking into this and decided to do some research as I like to do so I can formulate my own understanding and opinion on the matter. I don't care too much on tradition, (fiddler on the roof taught me that). If two people want to come to their own agreements and define their relationship then so be it.
So after reading
https://submissiveguide.com/dsrelationships/articles/collars-2?series=series-collars-and-collaring, a little I have gathered some helpful information.
I feel everyone should have CLEAR communication on what the details of their relationship should be, collared, owned, or other to make sure you know if you can still be open or not. There shouldn't be any room for misunderstandings.
I also think some get confused due to the fact that some who are married, collared, owned, or other on here are still able to play with others.
I think clear statements in your profile, that you think someone will read, should state if you are open to still play or not.
I feel the "collared" section on here should be used to place the persons name whom you are with as I see many do. This allows you to see who they are with and that it is serious, public, and let's everyone know you are taken and if someone oversteps then the one whom they are with will clap back.