I can sorta understand symbol sources, but why do we need to manually mark symbol languages? Can't we just use whatever languages have been indexed?

@joshuaspence - I think we've discussed this in private already, but just for completeness:

saying a file have symbol links adds the underlined-by-dots-link-like behavior; When it was first introduced, they were more link-like, and prevented double-click-to-select-word, which is even more useful when the reviewer knows the file is in a language we don't even index. I think that off-by-default configuration is a relic of that push-back.
Today, the link-like feature lets you double-click to select, albeit it might not be obvious to new users.

There's also the general issue that symbol detection is actually in shambles for many languages (Including Python and Java).

I'd vote to remove the language selection (Possibly adding a "disable all symbols everywhere" flag), because:

• I think the "like a link, but you can double click it" is good enough for everybody; New users will have to be told once they can do that.
• Product-wise, I think having linked symbols, in reviews and in diffusion, is very valuable. I use it constantly where it's available, and miss it when it's not.
• Having it more exposed might help improve it's quality, eventually.