That makes sense, but I think the “right” move actually depends on how these are marketed.
From a user perspective, are these truly standalone products, or is this one company with two offerings?
If they are marketed as separate entities, I’d argue for keeping the communities apart. If you force them into the same space, it can quickly become a case of “what do I post where?”. Users in Product A shouldn’t have to filter through a feed full of Product B questions just to find what they need.
My gut check for you: When a user gets a support email or an invoice, whose logo is at the top?
If they see themselves as a “[Company Name] user,” one community works. If they see themselves as a “[Product A] user,” or a “[Product B] user,” merging them might feel like clutter.
It’s almost always easier to merge 2 thriving communities than it is to perform “surgery” to separate 2 entangled communities.