Using arrow keys while focus is inside the Comments text box forces a page turn

After reading the first issue of Modern Frankenstein, I wanted to comment on the story.

I entered text into the comments box and while the focus was still within the box, I tried to use the arrow keys to navigate my comment to correct a spelling mistake.

Instead of the cursor moving, the overall page navigation function took over and forced a page turn instead of allowing me to move my cursor.

OS: Windows 10.0.19042
Browser: Brave Version 1.31.87 (Note: the issue occurs when extensions/plug-ins such as uBlock Origin are both enabled and disabled)