I guess I’ll kick start with the first reply 
In my current role, the community team sits within marketing, and I think there are real benefits to that. It gives us a strong connection to positioning, launches, content, advocacy and the wider story the company is trying to tell.
But, I’ve always felt that community is not traditional marketing. There’s obviously overlap, but the operating logic behind them is different. For example, what works in an acquisition funnel does not necessarily work within the community itself. Sometimes the right decision is not the one that creates the most immediate engagement or campaign value. Sometimes it is listening, slowing down, and creating space for feedback, or protecting trust even when that is harder to measure.
For me, the biggest challenge of sitting within marketing is making sure that community does not get reduced to “another channel”. Because community isn’t just another audience to broadcast to.
I think this model works best when the community team has the autonomy to make member-first decisions, while still being closely connected to the teams it serves.
All in all, I’m not sure the answer is “community should sit in X department”. I think the more important question is whether the organisation gives the community team the mandate, access and trust to operate across departments. That said, I’ve only worked in an enterprise scale community, but I can see that for smaller communities reporting into the department that the community primarily serves makes sense. But once community is serving marketing, product, support, success and education at the same time, I can see why more independent community leadership becomes valuable.
Otherwise the risk is that community becomes shaped by whichever department owns it, rather than by what the community actually needs.