Trello board permissions: Who can modify my board?

[Margie Roginski]

Someone invited me to be a member of their board and I noticed that I was able to add cards to their board.  

Where are the permissions that control this? I don't want someone to be able to modify my board in any way, either by adding comments or by adding cards or moving them around.

Under "..." for the board, I see "Commenting Permissions" and "Add/Remove Permissions".  "Add/Remove Permissions" seems to be for adding and removing members of the board.  Where are permissions for actually modifying the board?

[Iain Dooley]

@Margie Roginski If someone is a member of a board, they are able to do everything on that board.

You have the option of:

1) Adding someone as an observer (for boards in a Business Class team)

2) Having your board team viewable but without the "self-join" option enabled so team members can see a board but can't interact with it (you can optionally enable them to comment)

[Margie Roginski]

Thanks for the info, Iain!  Where is the "self-join" option that you mention?

Thanks!