Looks like you got some unwanted attention :))
I don't know about the technicalities and the cost to the blockchain, but I just do my thing and ignore the noise.
I am one of six kids...all born within 6 years. I think I learned to just ignore stuff I don't like. That was a survival skill in my house.
Yep. I just block them and you can block too. By using the ignore/block functionality they disappear. For example Ecency says this post has 15 comments but I only see 2, I assume the 13 others are by accounts I blocked.
Still even if I don't see them, whoever didn't block them will see those annoying spammers. Still, public APIs shouldn't be abused.
Spammers are unstoppable but to do that they should run their own nodes rather than abusing public nodes to relay spam.