Bug 516111

Since the merge of the rich text bar, now formatting your messages textually using Markdown syntax results in the user-visible text being visibly transformed into formatted text before your eyes.

For example if I type "# Title" then it will become large and bold, and the "#" character will disappear.

This doesn't feel good to use. The characters I type disappear or get moved around unexpectedly, and I'm no longer confident in my ability to type a message with markdown-style formatting and have it look good when sent.

I would recommend splitting the plaintext entry UX from the rich text entry UX:
1. When in plan text mode, don't visibly transform the user's text. Instead display the formatting only when sent
2. When in rich text mode (by opening the rich text bar), don't allow creating markup textually e.g. using #, -, and so on. Instead require interacting with the buttons to turn text into rich text formatting, as when using a word processor