One of my members reached out with the following:
 

  Quote

when I create a topic the advanced editor is available with all the features such as fonts, spoiler, text color, etc but when replying to posts only the basic editor shows up with stripped down functionality.

Is there a setting I'm missing, when I personally tested this out, the full editor shows for me whether I'm replying or creating a topic.

They would be the same editor unless you are using a custom theme, which for some reason, changes this. The only thing which would change what buttons are available in the editor toolbar would be the size of the window.

You would want to review the available sizes and ensure you setup what you want available to those:

I asked my member a few questions trying to pinpoint why the editor was different when replying vs creating a topic, he said after he tried different browsers on his laptop, it was only Firefox that was having the issue. The editor was working fine on the other browsers he tested.

When using Firefox was the browser in full screen mode?  If you want to see what we are talking about… try resizing the browser window to be less wide. Eventually buttons will disappear when you reach the medium width (like tablets) and even more will disappear when they reach the small width (cell phones).