The city does go after the people illegally tagging properties: https://sfstandard.com/2024/10/17/san-francisco-prolific-gra...

https://sfdistrictattorney.org/prolific-tagger-charged-with-...

https://sfist.com/2016/01/25/prolific_tagger_fined_over_200k...

Many more results if you search for “prolific tagger San Francisco”.