This is a great article, although of course there are a few things to quibble about. One that stuck out to me was this: "One of the inventors is Ken Thompson of Unix and Plan9 fame, and he was indirectly involved with C as well."
I'd have to say that Ken Thompson was directly involved with C, not just indirectly!
Well, Ritchie is normally credited with the creation of C and Thompson with its predecessor B. You're probably right, with the two coworkers working closely together on Unix Thompson probably made a lot of direct contributions to early C. But it was Ritchie that took C as his project and shepherded it through its growth and standardization.
Certainly Dennis Ritchie is the primary author of C, but given the very close historical relationship between C and unix, we know that there was a tight synergistic evolution that shaped each in relation to the other. As an example, very early C didn't have structs, but Thompson clearly needed a bit more powerful abstractions for some of the work on converting unix into C from pdp assembler, so Ritchie added them.
I was really just quibbling over definitions and connotations, when I hear of an "indirect" involvement I think of something very different and much more remote than the deeply intertwined stories of unix and C and Thompson and Ritchie at Bell Labs in the 69-74 era.
Also, "of Unix and Plan9 fame"... I accept that his audience and HNers may feel just as home with Plan 9 as they are with UNIX, but the wording suggests that these two systems grant the same level of fame, which is a wild stretch!
I'd have to say that Ken Thompson was directly involved with C, not just indirectly!