As some have already mentioned, a proper voting system should only allow a certain number of votes that you can dispense. Those who bought a license could have some more votes to dispense, but that is debatable. My idea here was that these users are more probably those who care about the software and use it, and who actively support the developers, so they should have at least a little bit greater say. But developers should not be thought of as being obliged to implement what the license holders or the majority wants. If that would be the only measure, we would end up with another mass market product like OneNote or Evernote instead of an innovative, powerful tool for knowledge workers.
Another important point is that the list of features should be curated - duplicates should be closed or merged together, features that have already been implemented should be closed etc. This is a bit difficult when using forum discussions. Though I must say the discourse forum software used here is awesome - great choice. And I just noticed that merging forum posts is actually possible and already practiced here. So after all, maybe the forum is in fact sufficient. More important is that the forum/list is curated and maintained by somebody.