Case
We have noticed 2 issues with email replies/signatures in our system. The first is if you click reply to an email you're shown code at the start of the email.
And the second, if you change the FROM address it removes everything from the email and replaces it with code.
Solution
The issue is that it was chosen to display not formatted text. The template itself doesn't contain the code, but when you choose to show bare text HTML formatting is shown as well. When we chose to display a formatted text it was displayed correctly. It can be chosen by the left Aa button above the text window.