How to Prevent .htaccess from Being Overwritten by WordPress
You can safely customize and control the behavior of your WordPress apps by entering instructions into each app's .htaccess file. However, the placement of your instructions is important so WordPress won't overwrite them.
To prevent WordPress from overwriting your .htaccess instructions, be sure to enter your customizations before the lines:
# BEGIN WordPress ... do not put any customizations here ... # END WordPress
Everything between those lines will be overwritten by WordPress.