Personally, I think I've only done the comment & link approach in cases where I had written something that related to the topic of the post I was commenting on. Of course any rule has exceptions, but I generally apply the reverse rule in comments. I only click links that appear to be related to whatever I was writing about.

I'm not considering flagging, but I am considering a policy of muting the follow for follow and other spam comment folks. I haven't done it yet, but I might start.