The short answer is we send plain emails so they are easy to parse when people reply to them.

What about a new mode: HTML vs plain?

Can you explain a little what problem we are solving?

People using my phabricator instance complaining about the emails. They say they are unreadable, and they ignore the content and just click on the link shown.

They also mention they are too frequent, but that is a different issue

Can you find out specifically what email (from which application, which actions) that they are having troubles with/ We are happy to look at specific cases.

Making them "more readable" by sending HTML is debatable as to it's outcome. It seems most likely an onboarding issue, one that doesn't exist once people are up to speed on the workflow.