Apoplexic is recorded as having downvoted 5787 before 5168 was posted.
Screenshots of vote records and such below.
5168 was posted ~16 hours ago at time of posting according to wikidot when I mouseover revision zero.
Screenshot.
5787 was downvoted yesterday at 14:31 according to SCUTTLE, which functions on some kind of American timezone. Any American timezone, except possibly Hawaii puts that definitely more than 16 hours ago, and aligns with Apoplexic's claim that he downvoted the article shortly after it was posted.
Screenshot.
EDIT YET AGAIN: Looking at SCPPER, it appears a vote was indeed changed and then changed back, but I don't think this is clear evidence of malicious downvoting given that the original vote seems to have been negative.
SCPPER screenshot 1.
SCPPER screenshot 2, which notes the update time. This appears to be between SCUTTLE scans, not sure if it's local to me (Ireland) or some other timezone, but that's hardly relevant.
TLDR: Evidence says Apoplexic had initially downvoted, then upvoted, then downvoted again since "03:41 today" which, whether an American timezone or my timezone, does indeed place it after the creation of 5168.
I'm not sure this qualifies as malicious.
Traditionally, we've had a very high standard of proof for that particular offence and, while downvoting after receiving a negative comment can come off as malicious, returning a positive vote to its initial negative state seems less so, to my mind.