I have,, for a while now, been made aware of similar practices and been suspicious of a few "new members" who have appeared on the forum starting new threads and posting within minutes of joining only never to be seen again.
There are red flags and signifiers sometimes when this is happening and I am unsure whether this is malevolent or mischievous. When my suspicions are raised i attempt to investigate further, my abilities are, however, limited.
There did seem to be common denominators between a few with a "fandom/comic book/fantasy" connection and others with connections to the "grunge/Indie" music scene.
When I have my suspicions I have pressed the report button or contacted a moderator voicing my concerns.
Personally, i don't think there is anything other than a mischievous motive to this particular practice.