As @Shadow Wizard points out, all of the un-upvoted posts have been edited, so it is likely to have been malicious un-upvoting. Which is a bit like serial voting, and wrong.

However, a list of "undownvote" or "unupvote" can appear in a reputation tab for another reason.

I have seen one case of serial downvoting, where not all of the serial downvotes were caught by the script. When Stack Overflow was alerted to this, the serial downvotes were reversed by un-downvoting.

Note that the other parts in the reputation tab are a day earlier. The voter can only have downvoted if these posts had been edited since their original upvoting.

So, it may be a case of a moderator manually reverting serial upvoting (whether by a third party or the OP themselves).

As @Shadow Wizard points out, all of the un-upvoted posts have been edited, so it is likely to have been malicious un-upvoting. Which is a bit like serial voting, and wrong.

However, a list of "undownvote" or "unupvote" can appear in a reputation tab for another reason.

I have seen one case of serial downvoting, where not all of the serial downvotes were caught by the script. When Stack Overflow was alerted to this, the serial downvotes were reversed by un-downvoting.

Note that the other parts in the reputation tab are a day earlier. The voter can only have downvoted if these posts had been edited since their original upvoting.

So, it may be a case of a moderator or developer manually reverting serial upvoting (whether by a third party or the OP themselves).

This is not necessarily done by the original voter.

I have seen one case of serial downvoting, where not all of the serial downvotes were caught by the script. When Stack Overflow was alerted to this, the serial downvotes were reversed by un-downvoting.

Note that the other parts in the reputation tab are a day earlier. The voter can only have downvoted if these posts had been edited since their original upvoting.

So, it may be a case of a moderator manually reverting serial upvoting (whether by a third party or the OP themselves).

As @Shadow Wizard points out, all of the un-upvoted posts have been edited, so it is likely to have been malicious un-upvoting. Which is a bit like serial voting, and wrong.

However, a list of "undownvote" or "unupvote" can appear in a reputation tab for another reason.

I have seen one case of serial downvoting, where not all of the serial downvotes were caught by the script. When Stack Overflow was alerted to this, the serial downvotes were reversed by un-downvoting.

Note that the other parts in the reputation tab are a day earlier. The voter can only have downvoted if these posts had been edited since their original upvoting.

So, it may be a case of a moderator manually reverting serial upvoting (whether by a third party or the OP themselves).