Recently I became aware that I prefer working with people who had previous work experience as testers. For example, I worked with a product owner who had advanced testing knowledge and I preferred working with that PO over all the others, who didn’t have a testing background.
What about the rest of the community? I’d love some thought on this topic! 
I totally feel this. A developer who had done a Testing job recently joined my team and they are excellent!
I agree, a couple of years ago I worked with a scrum master that spent many years in QA and he was by far the best Scrum master I worked with. He also knew how to implement change in teams which is a skill both scrum masters and QA leads when building processes
Totally agree. Working with PO who has practical knowledge is definitely a plus.
My personal bias is more of when a developer does spend time wearing a QA hat during requirements gathering and unit testing. It goes to show that the developer cares about quality and it’s proven with handover document(s) or proof of testing.