The browser extension is not their main product and they explicitly say so. The author is completely dismissing [0] the entire product just because of a side project, which in the worst case scenario could be fixed by the community by submitting a patch.
It is also strange that the author seems to feel the need to reinforce the sensationalism of this post by linking something completely unrelated to Keybase.
Also, where are the quotes on this post coming from? Where is the rest of the communication?
There is really nothing to see here.
[0] - "Initially, I planned to take a closer look at the crypto in Keybase, to see whether I can find weaknesses in their implementation. But that’s off the table now."
[1] - "But as experience shows (https://palant.de/2018/07/11/ftapi-secutransfer-the-secure-a...), the claim “end-to-end encryption” doesn’t automatically translate into a secure implementation."