Imagine the following. An Attacker manages to hijack your server. They fingerprint[1] the browsers of each user and only send malicious JS to certain users that dont use your extension. No one will ever know, that they have been compromised.
When you build and promote a system like this, you are assuming a responsibility on behalf of your users. You should take that responsibility more seriously.
EDIT: And you seem to be saying that this is actively bad, which I think is just jumping the gun without identifying any actual issues. Having it be only partially secure until you install a browser extension and then having it properly secure most certainly falls into 'good' and not 'bad' or 'great'.
You don't even have that. From what I can tell, you have literally no argument at all; instead, you "agree" with the article while drawing exactly the opposite conclusion that the article draws, then point out again and again how much users don't want to install things, as if that changed the security of this system at all.
Scramble performed encryption on the server, then my argument is false. But the design of Scramble's protocol is such that the security of the application depends only on securing the client code, which I argue can be done, for those who set up their environment correctly.
As mentioned in the writeup, there's a beautiful way you can protect even non-power-users. Because the extension downloads and verifies the webapp HTML, CSS and JS every time it runs, the web app is constantly being validated.
As long as you have a critical mass of power users who installed the extension, an adversary cannot tamper with the web application without immediately being noticed.
A strong adversary could still commandeer the server and serve tampered JS to a specific IP without being detected. Users who are specially targeted by such an adversary must either install the extension, use Tor, or both.
My goal is to make Scramble usable by a wide range of people. For a nontechnical user, it's just as easy as using Gmail--and at a minimum, they get the advantage that Scramble servers never store plaintext.
A user with stronger requirements can do more, and can get stronger security guarantees.