It's not just custom memes. I've not had a problem with that. I did a NSFW that was featured. It has the word sex in it. But this one: <a href="https://imgflip.com/i/1epk07"><img src="https://i.imgflip.com/1epk07.jpg" title="made at imgflip.com"/></a>
WTF, Imgflip? No sex, no politics, no nudity. It has 26 views and 2 upvotes, since I started this account (I deleted my old one) it's the only one that hasn't featured. It's like they don't want anyone to have a 100% feature rate.