Multi-Site user profile issues when integrating across a Multi-Site

Hi – Doesn’t time fly!

I promised @PC some time back to post a separate thread relating to WordPress user profiles when integrating Appointments + across a Multi-Site so hopefully it would generate some useful discussion and potential solutions.

I suspect the same issue would relate to a number of plug-ins that can be integrated across a Multi-Site.

For ease of reference I’ve added the responses to date that were captured on the shared thread.

My initial question was:-

If we have a number of different clients using a multi-site does this mean that registered WordPress users of one sub-site on a multi-site has subscriber access to all other sub-sites on the multi-site?

i.e. They can view other subsites

Also if a user say registers with a name fredbloggs on one sub-site does this mean the same name cannot be registered on any other sub-sites?

If this is the case is there any workaround?

I ask because the clients would not be aware they were on a multi-site and may ask why a username is being refused when they know that there isn’t a user with that name on their site (part of the multi-site).