I note that since the Recent Reputation History Changes, the reputation changes are updated immediately and with more details. But, today, at one point of time, my reputation on Ask Ubuntu just dropped from 6395 to 6380. I tried looking into the cause but I don't see anything different. No accepted answer unaccepted. No rash of downvotes. It doesn't look like any of my posts got deleted. Just to clarify, I was indeed looking at the reputation history with the checkbox for Show removed posts ticked. I can't think of any reasons that would have resulted in the reputation drop. And, askubuntu.com/reputation showed 6380 at that point of time. So, triggering a rep recalc wouldn't have done any difference.
I am considering this a bug since it is not intended.
Does it help that I suffer from chronic OCD since I started using Ask Ubuntu and would always like to know exact accounts of my reputation changes?
(Since then, I have answered a couple more answers and gained some upvotes and reputations. So, my current reputation will not reflect what I am reporting.)
I'll recount my events so it is easier for debugging purposes. (All times in UTC.)
Friday 27 April
1500 After making a slew of tag wiki edits, I log out for the night. Rep count 6350
0000 Received another upvote before the UTC day ends. Rep count 6360
Saturday 28 April
0200 One of my answers is accepted and upvoted twice. Rep count 6395
0200 - 0630 Between this time, I lose 15 rep. I can't find the cause. Rep count 6380
Funny thing is, once I figure that I lost 15 rep, the previous day rep count ends as 6345 thereby invalidating my claim that I lost the rep.
0630 I whine in the Tavern that "i just 15 rep but i see no records of it in my rep history.[sic]"
0830 Received another upvote. Rep count 6390
1300 The question Nick refers to is created. Rep count 6390
1545 I created this meta question. Rep count 6505
Not to sound pedantic..