While I agree with the message, that the people should leave all centralized Social Media services, the big mistake here is concentrating a massive user-base on one instance (.ml) of one specific service (Lemmy) instead of spreading the influx towards many smaller, but still solid instances and federated services (PieFed, Mastodon, MBin).
Even disregarding .ml's reputation, if this post does reach a substantial user-base, the only thing happening then is .ml receiving a HoD and people losing faith in the Fediverse as a whole (e: spelling) due to this, sadly. :c
Seconded, it's probably the fan. You can be sure, after checking oil and coolant of course, if it makes the same noise when cold at 6000 rpm (obv. don't do this for long, just enough to confirm whether or not it's RPM-related), then if first scenario didn't give the right indication, check if the bike makes said noise when the fan just kicks on.