I’m sure there are some good reasons, but I don’t know what those reasons are.
I’ve noticed that sometimes the instance of the community doesn’t match the instance of the user who posted there, and I was wondering why they chose to post to that community instead of an equivalent one on the instance they joined. Are there pros and cons to doing this?
Does that affect interaction? Perhaps this is a difference between platforms? When I signed up to PieFed, I chose some interests and it automatically subscribed me to various communities, some of which had the same name but different instances (for example five different communities named “Games”). I don’t know much about how community discovery works on any of these platforms to be honest.
On Lemmy, it will definitely affect interaction.
Piefed has the consolidated comments view who can help with keeping all comments from a crosspost visible (for instance https://piefed.zip/post/181387 ), but Lemmy doesn’t have that, so posting on the most active community will usually get more answers.