I haven't gotten any "sub4sub" comments in a long time, but I imagine that's partially because my own channel is just that unsuccessful in general.
Regarding the point of whether people truly like your videos, in my honest opinion, most people don't care. The way I identify someone who truly likes your video is someone who watches it all, shares it with their friends, possibly leaves a sincere comment, and preferably offers to financially support the uploader somehow. Unfortunately, we all know how rare those kinds of consumers are on the net.