About recipients of the notification "KM Subscription Group: Article commented"

[bonsai]

Who is the recipient of the notification "KM Subscription Group: Article commented" sent when a comment is made on a knowledge article?

It appears to be set as an event parameter.

Is it a member of the group that owns the article?

[jcmings]

Start by looking at the Who will receive tab of the Notification record.

This will tell you which parameter of the event call contains the recipient. Then, in the When to send tab, locate the name of the event. You'll want to do a code search in Studio (System Applications > Studio > select the same app that the notification is created in) for the name of the event. If you have SNUtils installed, you can also do /code eventName. 

You should find something that looks like this (source) -

Based on which box is checked on the Notification record, you should be able to identify the recipients!