Per its definition: constructive user feedback should make the developer's work easier, not more difficult. Swearing is obviously bad (maybe not so obvious to some people). Screenshots, steps for reproduction, expected and actual behavior are the minimum, together with willingness to answer questions and try potential workarounds and solutions. Checklists are usually introduced after experiences with unhelpful tickets and PRs.

Granted, not all open source developer might be good at interacting with users. But expectations should be very low since volunteer developers only have limited resoures to spend per user. And companies behind open source projects obviously prioritize their paying customers.