==We assume that things we actively notice other people doing in public are representative of what everyone (or everyone in some category to which we've assigned that person) is doing. We don't notice all the people not engaging in that behavior because they're not noteworthy.==

Doesn’t this comment include it’s own set of biases?

Such as?

I think that what they were getting at is that people noticing and commenting on things is more noticeable than people not doing so.

Which would imply that there's a tendency to notice the noticing more than the not noticing, and, as a consequence, over-estimate how often people do it.

It's a good point.