You are assuming that that was the only issue with the cover art, and a significant factor in the decision to change it. There were other reasons to change the cover art, which were sufficient in and of themselves to do so, completely discounting any threats that may have been made.
It still isn't a threat to give a reason to not review a game, though. There's lots of reasons and it happens all the time.
Did you miss the huge repeat of this topic on Steam when someone commented that D:OS was using the original artwork for the Steam winter sale? Did all these powerful and influential people who 'forced' the change suddenly disappear? The details for the sale were set before the awards and nominations started coming in.
There were valid reasons to change the cover art during the kickstarter, some of which are not as applicable now given the difference in target audience (kickstarter at the time being fairly US centric) and the much higher availability of game information.
