This was there second attempt of the same transaction. It still took them 3 days to figure out and a higher fee paid out of band.

Increased Time, and money cost is the point, and is demonstrated here.

Yes.

You are free to run, or not run filters. 

BITC0IN

🤝

would you be in favour of more targeted spam filtering options in core that are off by default, but are better then blocksonly=1 (shutting the mempool off entirely) ?