Possibly related; might be an extension or alternative to: A user should just be destroyed network-wide automatically if it has no upvoted content and is destroyed on two independent sites by mods already
As already explained in the linked question, spammers tend to create many accounts, then a mod from each site may destroy their account. Destroying their account will also automatically impose an account suspension, but only to that site.
This feature request expands the site suspension to the network-wide suspension if the user has been destroyed on a few sites, e.g. 3 different sites.
What I think the difference from the linked request is the timing; i.e. when they only have a few accounts but are destroyed network-wide, then they can still create a new account on the rest of the network and not suspended. This request intends to prevent future active spamming on other sites instead of cleaning passive profile spam (which the linked request may be more efficient for this).