Similar to liking, it should not be possible for users to vote for their own suggestions. Would a user make a suggestion if they didn’t support it themselves? Isn’t it more the vote of the other users that is needed here? In my opinion, that doesn’t really make sense. Therefore I suggest that a vote of the user who made the suggestion is not possible.
I would imagine this is baked in to how Discourse works and I would be surprised if it was configurable
option. I believe the plug-in being used would be this one Discourse Voting - plugin - Discourse Meta
To counter the suggestion, from a Technical implementation choice, I think makes sense if you think about the Vote as a counter it is adding to the initial value at the time of creation, otherwise you need internal logic to to either always include “+1”.
This also leave the possibility that someone could remove their initial vote after some discussion that changed their mind, but you wouldn’t necessarily just want to delete the suggestion as that removes the historical conversation and/or if other users still wanted to vote for it.
The behavior is also similar to other services such as Reddit so you potential have the battle of familiarity to contend with.
At the end of the day if the base is 1 or 0, it has the same meaning when applied across the board.
I have to agree with @codemonkee here. It is indeed baked into Discourse as well and I’m not sure it is worth the effort to change that