Let us assume User X had made a Community Wiki answer. While the post was still Community Wiki, it gained 4 upvotes (supposedly +40 rep). Then suddenly for some random, reasonable reason, the post was un-community-wikied. Of course, a community wiki post don't make you lose or gain rep regardless of any votes given. But a normal answer will. So I would assume all rep that would have been lost or gained will be applied to User X but I'm not sure. So my question is, after converting a community post into a normal post, will the original user lose/gain rep from the votes it acquired during its time being Community Wiki?
When the community wiki is removed from a post, the system "forgets" where the wiki even took place in the timeline of the post. All votes that came in after that point will thus begin to count again.
Removing the wiki will trigger an automatic recalculation for the user involved to calculate their new reputation score, which should be done within about 15 minutes-ish (it's not immediate).
However, you will not notice anything in your reputation history. It does not create any sort of "wiki removed" event for today. It will only modify the vote events (from whatever days they came in) to now count for the reputation gain/loss rather than being blank.