Currently, we can only vote for policies, which doesn’t provide as much useful data as having a vote for and a vote against button. In a democracy, the ability to dissent is just as important, if not more, than the ability to assent.
Alternatively, a 3 button setup could be useful, with the 3rd option being some sort of “Amend” button, that would allow people to indicate they agree with the idea overall, but would want to make some amendments. They can then use the replies section to elaborate on that if they so desire. I think this encourages alternate ideas on execution, and promotes civil disagreement.