This is very good insight and I definitely agree. With regard to your first point, I'll look to add a limit to how many users a person can message per day.
I spent some time already and plan to spend a lot more on moderation tools to mitigate the effects of your second point. Ideally fake profiles can be both reported and detected, but as of yet I have not invested too much time into these efforts, other than adding basic reporting features and a moderation page for those with sufficient power.
I tried to mitigate your third point by only allowing users to see your total cluster vote as opposed to your individual card votes. As a result, there is a bit of plausible deniability as your vote for each card is somewhat masked by the average. This could be furthered by reducing the cluster count and thereby making each cluster larger and mask more individual card votes.
I spent some time already and plan to spend a lot more on moderation tools to mitigate the effects of your second point. Ideally fake profiles can be both reported and detected, but as of yet I have not invested too much time into these efforts, other than adding basic reporting features and a moderation page for those with sufficient power.
I tried to mitigate your third point by only allowing users to see your total cluster vote as opposed to your individual card votes. As a result, there is a bit of plausible deniability as your vote for each card is somewhat masked by the average. This could be furthered by reducing the cluster count and thereby making each cluster larger and mask more individual card votes.