I am not sure if this is a bug, though it likely could be, as I had recently discussed with user "Mr Zak". The idea is to save the file, even though "Freestyle" is checked in the Render tab, then reopen the file. You may notice "Freestyle", in the Render tab, is now unchecked. ...Strange, huh? Check Freestyle again, then render it. Confused? So am I. However, this is the current working solution, and while Mr Zak pointed out he was using 2.78a, I am currently using 2.78c, at the time of this post.
Edit 6 days 55 minutes later:
I feel like an idiot, but I needed a minute in Blender's Discord to find out the fatal mistake: ...Pressing the wrong render button.
...You read me correctly, I was pressing the wrong render button, this entire time!
This is the button I have been using to render, this entire time. As the locals in Blender's Discord have informed me, a detail I have been overlooking for too long, much less to begin with, this renders OpenGL. That means you will be given a render of exactly what you see in the viewport, completely different from when you look in rendered view.
The buttons circles in this picture here, are the buttons you should be using for final renders, as opposed to OpenGL giving simply previews. That means that the button circles in the top-left section and the button circles on the right-hand side act as final render buttons, the equivalent of pressing F12 on your connected keyboard. Meanwhile, pressing the button underlined in this picture, and pressing the button depicted in the previous picture, will render only what you see in your viewport. If you want to see Freestyle lines, as I have been seeking, you want to use F12 render.
In case anyone is wondering, I have been asked if I had messed with the keybinds. I am not sure if this has anything relevant to do with it, but no, I did not mess with the keybinds. I have simply been blindly using the OpenGL render instead of F12's render, believing to have achieved the same results. I hope this proves educational and informational to anyone else who would ever make the same mistake I have made.