It can be confusing to know and understand the consequences of a user being added,removed, or blocked from a conversation. So hopefully this scenario and q&a will help clear things up.
Background: User A and B are in a group conversation.
Scenario 1. User A adds User C to the conversation.
Q: Will User C see the conversations history between User A & B?
A: Yes, User C will see all the messages between User A & B.
Scenario 2. User C then leaves the conversation, but user A & B continue sending messages. User C then re-joins the conversation at a later time.
Q: Will user C see the messages between user A & B?
A: Yes, when User C re-enters the conversation they will see all the messages in the conversation. Even ones that were sent when he wasn't in the conversation.
Scenario 3. User A is offended by something User C says, and decided to block User C.
Q: What happens in the conversation?
A: After the block:
- User A will see messages from only User B
- User B will see messages from Users A & C
- User C will see messages from only User B
Scenario 4. User A and User C make amends and User A then unblocks User C.
Q: Will User C then see all User A's messages that were sent while they were blocked?
A: No, User C will not see the messages from User A while they were blocked. After the unblock, they will start seeing messages from User A again.