Rules don't exist if there aren't consequences.
Their lawyers care about trademark violations that dilute their brand.
wouldn't be a trademark issue in that case, can you try your rebuttal again
It just really isn't that difficult for people to respect trademarks: we should not have sympathy for violations that are this blatant. HN should really not even be leaving it up, and they could themselves be served with notice (and yes: I realize that YCombinator invested in reddit; the result would just be some request in the backend); their strong and intrusive content moderation policy means they don't have any argument that "this was just user information".
(And if anyone from reddit is digging for examples of consumer confusion: when I saw "Reddit Grid" as I scrolled by, I absolutely had a first reaction of "oh, reddit is releasing a new feature to improve browsing? cool!" before remembering "oh yeah, people tend to be shitty about respecting trademarks, so watch this just be someone who wanted that official-sounding connotation".)
The bigger risk is that they'll come after you for using their trademark, but there's some PR risk to that too...
How does this work?
Android and iOS make it quite simple to grab the relevant APK or IPA packages as needed, then you just load that package into the appropriate decompiler or disassembler, look for strings first as often API keys are just left in as hardcoded strings.
It's not a recommended strategy if you want to be legitimate, but if you're going rogue anyways, may as well go all the way.