Posts to multiple instances?

I am wondering at the moment how to handle the different communities on the various instances that are covering the same topic: For example there is a technology community on nearly every instance. If I now want to create a post, do I just post this to one instance to avoid spam (I think most users are subscribed to multiple technology communities like myself) or is it better to post it to multiple instances to create more content and also support smaller instances?

At the moment I lean towards only posting to one instance, because I think there is no way to hide/ignore a post in the feed, when it shows up multiple times.

What do you guys think?