Idk if you noticed, most likely you did, but the marathon symbol showed up in spartan ops, episode 9, chapter 5, in the last section. Most of you know your bungie history, but for some that dont, marathon was a mac game released in 1994 then became open source for all operating systems in 2001. The symbol shows up in all marathon and halo games, except halo wars. And since 343 gained rights, id expect 343 to create a replacement reclaimer symbol that looks similar, which is seen in the campaign, but when I came to the switches in the end, I was shocked that 343 would put that there!
It’s been explained that the “Marathon” symbol is the Forerunner glyph for “Reclaimer”, in other words, the humans. The Librarian, was using it to either catch Crimson’s attention, or to hint at something else.