It's hard to build data to know. I haven't really bothered myself, because wall notifications I think only work on desktop, not mobile, so most people won't see it? (Not 100% sure, but I think that's the case).
I don't know if I'd get more subs if I did, but I think it's telling that when I look through who has left them on my wall when I sub, it was all comics which were below 200 subs (Bloodclot has probably got over that number now, but I subbed when it was really new and below 100). I can't even imagine having to post on everyone's wall when I had staff pick and gained over 200 subs in a week.
Basically, it's a nice thing to do and if you want to do it, it won't be harmful, but not doing it doesn't seem to have had a particularly negative impact on my comic's growth, and the comics that do do it don't necessarily show impressive growth over their peers.