Most of what I was about to write is similar to Kendra's answer on the MSO dupe noted in the first comment:
...in my opinion, badges for reading something are kinda pointless.
...we can't be sure that you've read it...
Honestly, I also find the "Informed" badge to be pointless, but there it is.
In addition to gameability, not everyone really needs to read the tour for each and every site to be able to be productive members; the same goes for the Code of Conduct.
In fact, since many people read docs like this only when they're linked to it after some issue, it could give mods/others some indication when and how they've been mod-messaged and how they responded, which is... kinda creepy.
Also worth noting that this would break the long-standing tradition of badges on a given site being exclusively for actions on that site. That is, reading the Code of Conduct would (presumably) get you the Well Behaved badge on every site you're a member of, whereas reading the tour for, say, CiviCRM SE gets you the Informed badge on just CiviCRM SE.
