Excellent suggestion! If there was some kind of screen that asked if someone was sure they wished to do a down vote, and gave them an opportunity to clarify what they had in mind, that would be a big improvement for the recipient--and often for the voter, too.
Apparently, many people hit the 'down' vote without meaning to. Some of them later discover this has happened at some point, and wish to change it--and it is possible to check back through recent activity and make changes, but sometimes these accidental keystrokes are hard to find if they happened a long time ago.
Here's a link to an older thread where this was discussed, with answers and comments by some WikiTreers who accidentally made down votes, and then attempted to rectify the situation:
Help! I gave out four down votes today and it wasn't my intention!