Strange mempool glitches

If you go watch my mempool statistics, you may have noted some strange behaviour in the 7 Gwei stripe:

https://mempool.jhoenicke.de/#ETH,1w,weight,6

First, there are several glitches where transactions vanish for a minute and then come back. (Ignore the single big glitch on Saturday, that was the update to geth 1.10.20). Moreover the stripe wasn't emptied, even when the 6 Gwei strip was completely emptied.

I investigated a bit and found the culprit. You may guess when comparing with the "by count" statistics these transactions are big. Someone has been sending transactions at 7 Gwei with 29.9 million gas limit, e.g. 0xb4f3c623af7a0e206f506f7743c3ec306ee51ab6aeb09adfee45d29836548862.

The glitches are caused by miners lowering the block gaslimit. Some miners vote for smaller block gaslimit and if they get a few blocks in a row, the limit will go below 29.9 million and the transactions will drop from the mempool, just to be readmitted when the next miner votes for 30 million again.

So why are these transactions not mined even when the fees went down to 6 Gwei? Simple answer: they don't fit. A single transaction paying more than 7 Gwei is already enough to ensure that these large transactions cannot fit any more into the block. So it is a stupid idea to go so close to the block gas limit with your transaction. If they were split up into transactions half the size, I'm sure they would all have been mined on Sunday, and the 0.1 % extra gas for sending more transactions shouldn't matter.