Feature summary: Using 'find' in an article should get hits from text in image descriptions. That is, whatever text is copied when you copy a page and paste it into a word-processor should also be searchable directly on WP without requiring that extra step.

Use case(s): on the https://en.wikipedia.org/wiki/Kaktovik_numerals we have Unicode characters that don't yet have font support. (I've submitted a font here on Phabricator, but that hasn't gone through yet.) Thus graphics are needed for display. The Unicode characters are present, but only in the coding. E.g.

[[File:Kaktovik digit 3.svg | x32px | 𝋃]]

That displays the character 𝋃 as an SVG file (since the browser isn't capable of displaying it directly), and when editing the article, 'find' is able to locate any instances of 𝋃, but when just reading the article, the browser 'find' function can't locate any instances of it.

This is an example. There are other cases where we use graphics for Unicode ranges that have poor font support.

Benefits: Currently, if you want to search where a character is, you need to copy the article (or a paragraph or table) and paste it somewhere else, or open the page for editing and search the coding. However, readers will expect to be able to search the article without any such workarounds. We're currently having a debate on the article talk page because some editors object to the 'find' function not working with these characters, and saying that graphics should not be used. However, if graphics are not used, those sections will be illegible. E.g. the Unicode character table will uselessly say that at code point 1D2C3 we have character 1D2C3, without showing which character 1D2C3 is.

Allowing the graphics to be searchable will mean that the behaviour of an article will be the same, whether the browser is able to handle the graphic display or whether we need a manual workaround to display some characters, as here.

Queston: it may be that only the title of an image should be searchable, and not the alt text. I'm not familiar enough with the difference to have an opinion on that. But when a graphic is used for a character for accessibility (say when reader font support is unlikely), and the Unicode point is also supplied so that the character can be copy-pasted, that character should show up in a search.