Thanks for asking. I try to help where I can, I try to answer questions if I know the answer. Sometimes I don't know how to help or can't always help.
Sometimes I'm not around on Imgflip. I can come and go around here as I please, so I'm glad to be replying to you here in a somewhat timely manner :)
The "Jeffrey" images by past and present user(s) have been around for a while, since late 2016 from what I remember. I would say there are also a few other users who have similar styles with their submissions and comments/replies, displaying scantily clad images of either male(s) or female(s) and/or both genders.
Some users feel strongly about such NSFW submissions and NSFW comments/replies made on imgflip and how younger users may be viewing those. I think NSFW content has made some users decide to leave imgflip in the past, which is not a good thing. We are sad to see users go.
I think a good approach is to comment and reply directly with the user about their style.
It seems like most users are reasonable and are willing to discuss their content with community members in a level headed manner.
It looks like you were and are on the right track here imgflip.com/i/2rmciu
Sometimes other users are not willing to discuss or adjust their style from community interactions. When content and conduct are clearly and purposefully outside the Terms, Imgflip can and does take action. Personally I don't think the content there is over the line, it"s just offensive to some users. That's just my opinion and viewpoint.
Of course voting up or down is up to the individual users, it's part of the DNA of Imgflip. Flagging can be a little trickier, before I was a MOD I used it rarely and only when I was confident an image or comment was clearly outside the Terms.
I know you've seen it, in general when users are confident there are repeated occurrences against the terms, one of the best ways to bring it up to Imgflip is to use the feedback form, you can send details via imgflip.com/feedback
also there is a feedback tab on every image page and most other imgflip.com pages. Those feedback forms do get reviewed.