I find this really weird. Recently, I switched from Chrome to Firefox, aside from not being able to use syntax highlighting or risk completely butchering my editing session, when I copy and paste a page title (or any formatted content on Wikipedia), instead of giving me the prompt like Chrome where it asks me if I want to "Convert to Wikitext" or "Use plain text" It pasts in the Title, with its formatting and underline, then prevents me from making any edits or removing the formatted title. See attached screenshot. My browser details are here.

1. Open the 2017 Wikitext editor on Firefox
2. Copy a title or other formatted content
3. Paste it in to the editor
4. See results

Actual Results:

• The title cannot be removed when highlighted or using the backspace
• The whole editor breaks weirdly and glitches, and anything you type after you have pasted in the formatted content fails to save and does not publish when saving your changes.

Expected Results:

1. Asks if the user wants to paste as plain text or wikitext, similar to the behaviour in other browsers
2. Allows the user to remove the formatted content and continue editing