Yes. Just like users, communities are defined by their fully qualified names. So Games@mydomain.com and Games@yourdomain.com are different communities, even if the “Games” part of the community name is the same.
There’s no way to like “merge” it though if that’s what you mean. So it’s possible you will have two “Games” communities you subscribe to for example. However, that’s not dissimilar to what happens on reddit already. /r/Games was born because /r/Gaming was going in a direction some people didn’t like. And then /r/TrueGaming was born because they didn’t like either of those. And you have small subreddits closing to point to larger subreddits, etc. Over time that’s a problem that will just naturally sort itself out, though the UI for creating/searching for communities could use improvements to help with that process too.
Is it possible to sync two same named communities across multiple instances?
Yes. Just like users, communities are defined by their fully qualified names. So Games@mydomain.com and Games@yourdomain.com are different communities, even if the “Games” part of the community name is the same.
There’s no way to like “merge” it though if that’s what you mean. So it’s possible you will have two “Games” communities you subscribe to for example. However, that’s not dissimilar to what happens on reddit already. /r/Games was born because /r/Gaming was going in a direction some people didn’t like. And then /r/TrueGaming was born because they didn’t like either of those. And you have small subreddits closing to point to larger subreddits, etc. Over time that’s a problem that will just naturally sort itself out, though the UI for creating/searching for communities could use improvements to help with that process too.