overuse would quickly make tedious even the cleverest

No kidding. The very short wikipedia article that jdporter links to even says:

This allowed the frequent use of preset text [...] which resulted in the "Timeline of history" image being banned from use

And my best guess is that inclusion of this feature and success at getting it used much at all would lead to most people wanting it banned. So the feature would either be almost never used or almost always hated.

Boilerplate is annoying. Implementing a way to encourage boilerplate pasted onto a "meme" picture just makes the boilerplate stand out more so you notice it more. This leads to what I call either "The Barney Effect" or "The Britney Effect". I actually enjoy Britney Spears for the most part. Barney (the purple dinosaur) has a few annoying traits. Living in a house with a very young fan of Barney or nearly just being alive a few years ago often meant being exposed to Barney and/or Britney way, way too often. The result was that both of these characters were widely and vehemently hated by a huge swath of the population.

Many people who lived through such now consider one or both of those characters to be some of the most astonishingly annoying things in existence. A single second of exposure to them leads to near-violent reactions. Neither of them is really that horribly annoying when you haven't been overexposed to them.

Putting meme pictures onto a site with such an understated style would mean the pictures would stick out like a sore thumb. And having a fixed set of repetitious boilerplate to draw from for the pictures would mean that even minor frequency of use would trigger The Barney Effect in many, I believe.

I mostly stay away from "meme pictures" compared to your average internet user, I suspect. And yet I already find them quite banal. I don't look forward to having the already-too-common boilerplate responses that I find annoying at PerlMonks being blasted into my face with meme pictures so that the boilerplate becomes Barney and the meme pictures become Britney and the relatively few but still frequent times I run into meme pictures elsewhere I start having violent reactions instead of just sighing.

From now on, when you read a BrowserUk post, imagine it contains an "All your base" pun. After just imagining that becomes annoying, start imagining that the pun is in a font several times larger and bolder than the rest of his posting as part of a picture of Barney playing bass guitar.

And if you don't think there will be monks who find one particular "meme" way too funny way too often and will start pasting it almost every time they post, then I suggest you remember our dear, departed blazar. His trying to make me remember the Miss Teen Wherever candidate inanity about "don't have maps and such as" happened way too often and went on way too long to the point that it colored my whole perception of blazar. blazar is Britney Spears to me. I usually can't remember a single thing about blazar now other then "I personally believe" (but in bold) and that he died. And that makes me sad.

I shudder to think how much worse it would have been if "bold tags" had been replaced by a colorful picture of something goofy amid a rather drab two-color web site.

Yes, most of my references above are very "dated". That was intentional. Just about any meme picture will similarly seem very stale very quickly.

I find it unwise to make PerlMonks such that the thing that any casual visitor will remember, by far, about it is that some annoying puppy keeps saying "use strict".