For what reason? If they're enough of a scum to break the ToS, then they should be reported. Otherwise, it's largely irrelevant as you'll likely to not encounter them often enough to matter much unless you're both stuck doing the same niche contents, which is where the ignore function should be used if available.
The idea that people could be openly toxic means there is a lack of rule enforcement, which is bigger concern than knowing whether someone is a scum.