@folkert_hobma: Bummer to hear that. We’re working on SSO integration (for Enterprise customers) now, and following that are going to explore non-Google login. Due to our tight integration with Google Drive, looking into non-Google sign-in wasn’t possible until we built out workspaces and our own sharing and permission system.
Note that we are GDPR-compliant as a platform, and our collaboration model is very similar to Google Docs or Office 365 – you invite editors to a Coda doc using their email address. We only use such emails for the function of the service and per the analytics preferences of the users associated with those emails set on the trust page, in full compliance with GDPR.
We take security very seriously and have many safeguards in place against a breach, and in fact are working on SOC II compliance, one of the industry’s most stringent certifications. You can read more on our security page.
To your point about making mistakes with dates and amounts, as we’re getting more users outside the US (I know our country’s date formats are pretty wonky compared to the rest of the world 
), we’re also looking into internationalization, besides timezones and international currencies. It is going to require a significant amount of work on our end, however.
Lastly, if one of your editors makes a mistake, you can use version history to restore an older version, or if it’s on a row, you can see previous edits in row activity (where row comments show up).