Escaped HTML present in doc comments gets rendered in search results

[jdm]

By escaped, I mean stuff like

/// stuff for `<iframe>`

which renders fine in non-search listings (it looks like <iframe>, instead of a literal iframe element on the page).

[steveklabnik]

I thought we had an issue for this, but cannot find it.

[frewsxcv]

Relevant to inline summary rendering: #25787

[mitaa]

Search result descriptions aren't markdown rendered and read/written unaltered from the search-index to the page.

Should these descriptions be markdown rendered or html escaped (#18419)?