By the Grace of CCP gods… you can block entire alliances.
If you’re sick of the literal vomit into local chat ( jita of course being the worst offender )… just block the corporation or alliance of the character. Jita local will fall virtually silent after about 20 or so.
Chances are you never want to hear from those people anyway. It’s crude… but has definitely worked for me.
It’s by default on the avoid list for autopilot, not sure how it’s unavoidable. You can trade region wide and just move the stuff in and out, you don’t have to sit in the system.
The network traffic is the problem too, not just the visual text on the local chat window, imagine if you could stop the chat traffic spam, your client may be performing less laggy in Jita? So being able to actually close the window, might be benefitial.
On the Tech side… think of all the data points in the DB that could be eliminated and network traffic that could be cut. I still see the chat server struggling sometimes (disconnecting/reconnecting).
SPAM anywhere is no different than spam email. Just abusing DB resources - when it could be blocked.
But…but…someone is giving away their entire Eve fortune of 80bn ISK because their pet hamster died and they are too sad to play any more. Its an obvious bargain !