[koide]

I find hard to interpret "A 40 yo learned something from a 13 yo" in a non ageist way. Seems that people disagree, but nobody has provided a counterpoint.

Actually, the comment in question would have been perfect encouragement in my view just by removing that phrase.

[elendee]

I've only ever heard that term to mean bias against people considered too old for a given activity.

[koide]

That's the most commonly discussed form. There are others as in https://www.medicalnewstoday.com/articles/ageism

[andybak]

Just felt like a bit of an overreaction to me.