How to block a seller on Craigslist?

Question

This single user currently has 543 postings, all basically the same 2 ads.

They use keyword spam in the ad body to appear in substantially every Craigslist search I perform.

How can I block or mute a Craigslist user so that I never see another one of their ads?

If it can't be done via a CL account setting, how can I do so via an ad-blocker program?

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I'm aware of other potential solutions to improve my search:

• Filter "by Owner" so that I do not see any dealer results.
• Add -cargo or other similar negative search terms.
• Flag the ads by this user.

But this question is about blocking a seller entirely.

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