Imgflip defines Spam in the Terms of Use:
imgflip.com/terms
Spam is broad, not just links. One imperfect analogy to links on Imgflip is that they're like a yard sign or a billboard.
Someone placing political signs or advertisements on public or private property (with or without permission) might see them get removed. Maybe your neighbor or friend won't mind if you put up your billboard in their front yard, maybe they will mind. Maybe your friends neighbor minds the billboard you put up in your friends yard and they think it's against the local sign rules. This is just a hypothetical example/analogy.
If a user thinks a comment (with a link or not) is against the Terms of Use, they can flag it and a Moderator of that stream can take a look. Sitewide Moderators may find comments they consider against the Terms of Use on their own and take action by deleting them, with or without warning.
A user is solely responsible for their Content within Imgflip, regardless of whether information is requested by another.