That is not a reasonable stance. The picture from OP is not reasonably construed as "offensive content", and definitely not as "spam" (unless one person put like 10 of these up or something?). Even if one feels the joke is in bad taste, it is still just a basic price-complaint negative review, no personal insults/threats/whatever being hurled in that one.
Compare it to a generic "DLC costs too much for what it delivers, do not recommend". How is it inherently more offensive or spam than that? If it does not meet the standards of being worse than those types of reviews, then flagging it that way is uneven moderation by the devs. One review being flagged while others doing equal or worse are ignored is nothing in which to take pride.
Or if that does meet the standards of "offensive content", why AREN'T all review of similar standards flagged, and what about the actual in-game comet event and similar ones, which would probably meet whatever standard pdox could use to claim this review is "offensive"?
If this was just flagged for spam because he posted it like 5x it's another matter of course.
I think the explanation given by Paradox above is that the intent was to flag as "off-topic" but whoever did it accidentally flagged it as "abusive". I can see the reasoning behind off-topic.