"Good morning. Here is something awesome that you got last night!", said the Top Bar:
"21? That must be two answer upvotes and, um, an answer that I downvoted that was deleted?", I thought. Ok, let's look at the details and find out:
The +20 on my egrep
answer is new and I've seen the other Achievements on the list, so where did the extra +1 come from? In order to avoid confusion, the recent reputation changes in the dropdown should add up to the number in the notification.
I suspect this particular case is a bug. Assuming the +1 is a downvote reversed by an answer deletion, I could see the argument for excluding it from the Achievements dropdown. After all, it's not exactly something you accomplished. Except it kinda is. Part of the reason for downvoting is to democratically censor low-quality content. The ultimate sign that such content was deemed beneath community standards is when it gets deleted. I'm not sure that we should award a badge, but putting a note in your achievements in such cases seems like it would reinforce positive (albeit negative) behaviour.
This question is a feature request that rep gains from deleted downvotes be listed in the Achievements dialog, without getting into broader issues of displaying other activity on deleted posts such as those discussed in Reputation items in the achievements dropdown don't add up. Thus, this is not intended to completely address the issue of the Achievements sum not adding up, but is intended to help encourage good community moderation by appropriate downvoting of low-quality content.