i don't get why that other user is being such a lemmy ahh replier. i don't really use "ahh", but here's my working definitions.
"ahh" is slang that means "ass", but as far as i know, it's usage is restricted to when you would say "lookin", or when referring to yourself.
so "goofy lookin' shoes", "goofy ass shoes", and "goofy ahh shoes" all mean the same thing. this use doesn't work for positive contexts, though; "sweet ahh car" is improper.
also, "my hungry ass when i see burger", and "my hungry ahh when i see burger" mean the same thing.
a "lemmy ahh thread" thus means "a thread that is negatively stereotypical of lemmy".
i hope this helps :)
67 came from a song lyric, then a kid made a tiktok where he frantically said "six seveeen!! six seveeen!!" to the camera while doing a gesture with his hands. and because kids love pattern recognition, when they see the number it's easy to point it out and do the gesture. and so the meme spread.
the humor comes from it being nonsensical; the joke is on anyone who's either tired of it, or never found it funny at all, so i don't really see it going away anytime soon.