Someone coming from Instagram should have no trouble understanding why their posts to Instagram didn't show up on X, and someone coming from X should have no trouble understanding why their posts on X don't show up on Instagram. The same should translate to Nostr and understanding why posts to Olas, which is an Instagram ripoff, don't show up on "Twitter clone" clients.

It should further blow their minds when they learn that some clients can display both.

It doesn't, because users assume Nostr is like a platform, and that all clients on that platform should display all content the platform supports.

That said, I am warming up to the idea that kind 20 is superfluous, and we should just use hashtags to differentiate between memes, photography, and other forms of image-based media. There IS a distinction between kind 1 notes and kind 20, but it is small enough that maybe a separate kind isn't justified.

Kind 1 is a microblogging note that MAY contain image links, and kind 1 clients may or may not render those links as the images they link to, though most do.

Kind 20 is a picture and will ALWAYS contain an image link that supporting clients are expected to render. It MAY also contain a caption.

So, they are definitely different in how they function, but I agree that it can be confusing and kind 1 can fulfill the function of kind 20 and be pulled into a separate image feed if desired. Eh... I'd probably be fine with doing away with it after all.