I am surprised I did not find this feature request by searching the forums. Someone please point out another post of his feature request to me, if I have missed one. I tried:
- Two factor authentication
- 2 factor auth
- Multi-factor auth
Use case or problem
Account security is always weak when it is based solely on a password, no matter how long that password may be.
While Obsidian has only the 1 password security solution, all user data is under unnecessary risk. While the data may be encrypted on the Obsidian servers, the attack vector of the user (stealing their password via phishing or social engineering) bypasses this entirely.
Proposed solution
Two Factor Authentication as an option for logging into my Obsidian account. Both online and in the app.
Authenticator code is fine as a default (as it can be done for everyone with a phone) but a further option for Security Key would be much muuuch better.
Hell, even these forums have Two Factor Authentication for both Authenticator code and Security Key! I think my conversations here are a lot less important to protect than the entirety of my collected notes and thoughts 
Edit: also, 2fa would protect ones account from being taken over, including your purchased licenses.