Don't forget that also flagging requires some VP. If he has to either upvote or flag all the comments, it'll cost him a lot of VP just to organise his comment section.
I just say though, I feel like the 'nice post upvote me' comments have been reducing lately.
I am not only addressing him. Since this platform is decentralized, I think people need to wake up and realize that there is no central authority that is going to take care of spam. The users are the ones with the power to change this platform for better or worse.
As a result, each one of us has a greater power to contribute. Everyone could contribute in reducing spam by downvoting spam comments. A lot of people are trying to flag people like haejin but most of them don't have the SP to do anything significant. A better idea would be to focus on ridding this platform of shitty accounts because a lot of people do have enough power to flag someones comment to the point where it isn't visible and/or lowers that person's reputation score.
There are initiatives like @cheetah and @steemcleaners, but it is hard to keep up with the amount of spammers.
Steemit is a community driven platform and thus we have to stand up for eachother - but I guess the latter doesn't happen as often as we'd like to and/or we simply do not have enough power to make a difference like you mentioned.