Minh Nguyen proposed:
{{#ifeq: [[{{NAMESPACE}}:{{lcfirst:{{PAGENAME}}}}]] | {{:{{NAMESPACE}}:{{lcfirst:{{PAGENAME}}}}}} | | Did you mean '''[[{{NAMESPACE}}:{{lcfirst:{{PAGENAME}}}}]]'''? }}
I replied:
Oh! Splendid! I didn't know about those. I'll... try this out. Thanks very much.
With a bit of tweaking (see below), this seems to work perfectly. If you're curious, see
http://en.wiktionary.org/wiki/cypriot http://en.wiktionary.org/wiki/Tamper and http://en.wiktionary.org/wiki/nowordatall
for a demonstration.
I had to remove the explicit {{NAMESPACE}}: tag. For whatever reason, in the main namespace, that caused the comparison to always be false, making the page always seem to exist, whether it did nor not. But removing the tag makes it work perfectly for the main namespace. (Removing the tag breaks it in the other direction for the other namespaces, making the link almost always fail, and the comparison always true, and the page therefore never seeming to exist. But that's actually a good thing, in this context, since we probably don't want to display "Did you mean?" for minorly-different capitalizations in the various project namespaces.)
At some point, once Tim recovers from (or becomes inured to) his horror at sending us down this slippery slope in this hell-bent handbasket, we can think about introducing a proper built-in {{exists:}} operator, to eliminate the need for the bizarre compare-the-substitution-to-the-redlink hack. (Though I *am* appreciative of whoever devised it...)