You can turn it off:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(2) In the search box above the list, type or paste backs and pause while the list is filtered

(3) Double-click the browser.backspace_action preference to display a dialog where you can enter the desired value, then click OK. Your choices are:

• 0 = Go "Back" in history (default)
• 1 = Page Up
• 2 or other value = ignore the keypress

The problem is that this is the default settings for all users.

I'll bet it on my head that the destructive effect of this "feature" far out weights the ease of life for the few. 

Imagine if 'Enter' key would reload the page if one had not clicked in a text bubble. It's absolutely stupid, yet it's similar to the current situation.

Is there not a way to get this message to the top?

-Sincerely, someone who lost 3 paragraphs of text.

To submit suggestions for future Firefox features, you could use one or more of the following (depending on whether you want a suggestion box or a discussion):

• Feedback: https://qsurvey.mozilla.com/s3/FirefoxInput/
• Reddit: https://www.reddit.com/r/firefox/
• Twitter: https://twitter.com/firefox
• Facebook: https://www.facebook.com/Firefox