I can't say I've run into this because I use the app (^#Q&#@Q& about that app for several reasons), but this does feel like a very low blow. Especially since a lot of people resort to that because for whatever reason they can't get the app working on their phones. At the least (and I'm not saying this action is right or justified) at least it's the comments that are getting put behind a wall and NOT the comic pages themselves. (still not justifying it. Just expressing that I'm glad it's not worse)
In concerns to ads though, they have actually be placed within the app (I've been informed by a comment on one of my pages left by a readers, as well as I've seen them myself) they're a little clunky and can be sometimes awkward but they are there. (They also tend to confuse some readers into thinking that they can no longer read comments on the ap because of the way the ads are displayed, so it's still problematic and needs some work)