“What kind of image artifact lets us see the hand blocked by the microphone?”
Compression artifacts can cause extremely bizarre effects in video - because they distort time, not just space. The compression algorithm may choose to suppress data from faster moving objects or objects with less contrast (the microphone), and present pixels from the higher contrast or slower moving object instead (the hand).
In order to comprehend how the hand (which is obviously farther away) could possibly overlap the microphone (which is closer) it helps to remember this is a video - this is a time artifact, not a space artifact. The hand isn’t really “overlapping” the microphone, which would be a spacial artifact - it is just that the pixels representing the hand are stuck there as the microphone passes by the hand - a temporal artifact.
We have all seen weird compression artifacts where as a face moves, the pixels where the face should be are replaced with something else. That is what is happening here. Of course, the hand is never “in front” of the microphone - it is just that the data from the moving microphone is being compressed, and the algorithm is leaving pixels from the hand longer than they should be there.
Another way to think of it is to think of an effect where there appears to be a trail as something is moved. We have all seen that effect. Yet we know the thing is not really leaving a trail - it is just certain pixels remaining longer than they should.
Same with the hand, the pixels representing the hand should have been replaced by the pixels representing the microphone as it passed over the hand, but because of compression - the hand pixels remained - making it appear that the hand was overlapping the microphone.
Everything in this video can be explained by compression.
Look at the sequence at the 11 second mark when Biden is gesturing downward with a pointed finger on his right hand. How is this hand visible behind the microphone that has been relatively stable in the view?
-PJ