But a sharper question is: Can meditation be actually harmful?

The answer depends, of course, on what you mean by meditation. The word meditation can be used to mean many different practices, and I have no doubt that many of these are, or can be, harmful.

I think one of the necessary conditions for a meditation practice to be harmful, is that you are following a set of instructions blindly; the teacher said 'breathe like this, focus on that...' and you just do it, or try to do it, without really knowing why. And if you don't know why you are doing it, if it is not your own practice that you have developed, then you can twist all sorts of things around in your head and do yourself some harm.

But if you are gentle with yourself, don't step out if you cannot see where your foot will land, don't rush to make the uncertain certain, and keep that bullshit meter at hand, then I don't believe you will come to any harm - at least, to no more harm than you would if you did not do such a meditation, and the chances of doing yourself some good are very great.