Another suggestion for OP: Firefox for mobile contains a function known as "Reader View". Read about it here:
https://support.mozilla.org/en-US/kb/view-articles-reader-view-firefox-android. It essentially removes all the formatting, and displays just the post content in a large font wrapped to your screen size, which will remove the need for left to right scrolling. It doesn't help with navigating the site, but it makes reading threads much easier.
I like to trim them to the point I want to address and that can take several minutes to get the goddamn phone to delete the bits I want with disappearing cursors and over enthusiastic deletions.
Obviously this depends on what mobile handset and operating system you are running, but on my phone there is an option in the keyboard settings which pins a button to the keyboard which, when pressed, will hide the keyboard and display a "text editing" interface, which contains arrow keys for navigation, cut/copy/paste buttons, page up/page down buttons, select all, and so forth. It makes editing quotes and bbcode tags so much easier on mobile than the usual fat finger pressing trying to get the cursor in the right place.
There are also third party app which will achieve the same thing, but I would stay away from them since any keyboard or text editing app can by default act as a keylogger.