It is a form of moderation. It may not be as extreme as outright deletion, but it does make the comment harder to read, which is a mild form of censorship.

And, yes, I'm aware of why it can happen, and how one can deal with it. It's just a trend that's getting far worse than I remember it being. There was one Python submission I saw yesterday where probably 1/3rd of the comments were greyed out when I viewed it. It becomes distracting, and makes it harder to read the comments.

I usually end up reading them anyway, since so much legitimate and valuable content is now shown in grey so often. It defeats the purpose of displaying comments like that when so much good content has so frequently been mis-voted down.