I use a userscript that will like a video (even if not subscribed) if I watch at least 80% of it. As for commenting, it really depends on the topic. Like, if someone needs help on a tutorial, yes. General videos like PewDiePie, no.
As for subscribing, a channel’s content must be interesting and not feel corporate. It always feels good when you find a new youtuber you like!
Fucking hell that sounds painful