The admin of lemmyworld said it’ll take time to remove them, but I don’t know why (there seems to be the functionality in the API)
Indeed. Looks like it’s just a matter of a big for loop over each community ID, POST /community/delete with body community_id=1234. Maybe I’ll try to see if it’s possible to get some action on removing them by sending over some Python script or something that does the job. Quick count shows almost 14%(!) of all communities indexed by lemmyverse are those junk communities: