I don't know about how the photo was originally presented, but the tweet that I linked explicitly says the frame is "17 30-second images of the comet added up", so it's hardly disingenuous.
He's saying the photographer specifically stacked the frame to increase the interference of the satellites. The same basic technique can be used in either direction - astronomers already use it to remove the thousands of satellites and other causes of interference in the night sky.
No. A single long exposure would only show maybe one or two of those satellites. That's numerous exposures stacked on top of each other, such that every satellite visible in any of them is in the final result. This is completely backwards from how photo stacking is meant to be done (it's meant to remove satellites not visible in all of them.)
Very interesting, thanks for sharing this. This indeed should be pointed out clearky by whomever creates such images - seems quite manipulative using this to make a point.
The impact of Starlink on astronomical observation is in dispute and by no means is a settled matter: https://en.wikipedia.org/wiki/Starlink#Criticism