We can't use Ecency points to buy votes, so it's not selling nor buying votes. We can only do 3 things with Ecency points:

1. Transfer them. Like any other token.
2. Use it to promote the post in the main/trending feed. The same thing peakd does but we use Ecency points instead of Hive.
3. Boost, we can get a HP delegation for 7, 30 or 90 days.