I don't expect these features to be removed. You could consider using custom style rules to hide those items. Many aspects of the appearance of Firefox's user interface can be modified using short style rules in an optional file named userChrome.css (this file doesn't come with Firefox, you need to create it).

I created a sample rule set for you, and the attached screenshot shows the difference it makes.

• Hides the Reader View icon and the Page Actions menu button (•••)
• Reveals the hidden buttons if you hover the area for 3 seconds

Here's how to set it up (assuming you haven't already created a userChrome.css file):

(A) Create a new chrome folder in your profile folder. This article has the steps for that (#1, #2, and optionally #3)

https://www.userchrome.org/how-create-userchrome-css.html

(B) Download the following file and move it into that chrome folder:

https://www.userchrome.org/samples/userChrome-page_action_buttons.css

(C) Rename that file to just userChrome.css

If you already have a userChrome.css file, you can copy/paste the rules from the new file into the existing file.

The next time you quit Firefox and start it up again, it should discover that file and apply the rules.

You can disable reader via this pref on the about:config page if you do not want to use this feature.

• browser.readinglist.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config