I think there are some differences that make the fediverse more resilient to this. For example, the absence of cumulative account karma keeps out the reddit style karma farming. The ability to ban whole instances also makes it easier to kick out bad actors. Instance admins could also implement their own rules like switching to an invite based system to reduce bot spam. Also it seems to me that reddit is actively encouraging this kind behaviour to inflate their user statistics and there is no incentive to tolerate this kind of spam for a fediverse server admin.