Hi Bill,
Everyone on the AllStar repeater will hear you and you will hear everybody on the repeater. It’s just like you are within the repeater coverage area. Also, if there are other nodes connected to the repeater node, you will hear all the other nodes and they will hear you.
Here is a graphical example of a bunch of nodes connected together. Everyone in this group can talk to everybody else. This is the WIN system, which one of the biggest AllStar groups. This page takes a while to load.
http://stats.allstarlink.org/getstatus.cgi?2560
Here is the list of all AllStar nodes. The green background node number indicates an online node. Click that to see any connected nodes.
https://www.allstarlink.org/nodelist/
It is possible to connect in the monitor mode (*2xxxxx). This would allow your node to listen to the monitored node but they would not hear you talk. However, it’s unlikely that’s how the repeater your friend is on is setup to only monitor inbound connections.