Are vent clips safe for my car's interior?

Mostly yes, but reviewers on r/prius and elsewhere have flagged isolated cases of liquid vent-clip fresheners leaking and damaging vent plastic or paint. r/TeslaLounge threads also warn that wood-style diffusers placed on leather can leave oil marks. The safer move is to keep liquid clips upright, avoid mounting wood diffusers directly against upholstery, and remove them on very hot days.