Maybe they're trying to post in an unsupported language or a partly unsupported language? Also could just be sending out "test spam" so they can tell potential

Maybe they're trying to post in an unsupported language or a partly unsupported language? Also could just be sending out "test spam" so they can tell potentially clients that they have a n+1 list of sites which can be spammed for $50 (or whatever). You often have SEO companies in particular buying lists of spammable sites or spam companies buying lists from indexers so they can sell a service to SEO companies or the mob.