Thanks---ideally, one should use this, right? However, It's faster and more intuitive for me to head straight to "my rules" first and look at the code. If need be, I'll just uncheck that module and go from there.Learn to use the logger and you can pinpoint the source of the issue. It takes some time but is well worth it.
The line rain2reign posted was in fact the culprit but how it got there in the first place is a mystery. I must have zapped something on a YouTube page but what? Scanning the logger would take too long (for me). Hopefully, it won't happen again but my point was: if you see something like that (missing YouTube comments, etc), check "my rules" first--if you use the Element Picker.