How about schemes that are less obvious, such as communities receiving benefactor rewards from posters in return for votes such as olio de balena or membership schemes that return upvotes to its members' regardless of post quality, such as SSG.
Do other incentives such as HBD cashback schemes and large votes for using distriator count as buying votes? Or those rewards given for using the product rather than just supporting it.
As for HSBI, is it really that much different than auto voting from a human?
It appears there needs to be distinct definitions drawn up on what is acceptable and then absolute consistency in application without prejudice regardless of the account's size.
Happily, the .concencous is that vote buying is wrong but there are some dubious back scratching schemes going on that fly just below the radar.