dlanor,
Thanks for your explanation. But no, I'm very aware of the system writes to SD, as well as the function of PHT (it's what I use on my HTPC). In the settings, however, I do not see Reboot as an option. Rather, I see Quit/Sleep/Shutdown similar to what I have on my HTPC. I've gone through a full configuration of rasplex, and know what I'm doing there. For some reason that setting isn't as you're describing.
When I choose to reboot by unplugging the power to the RPi, I am smart enought to issue the shutdown command via rasplex. :)
FYI, I'm using 0.5.1 on the RPi2.
"Quit" and "Sleep" do not exist in any RasPlex release, so you must be mistaken.
Possibly you are using an unsuitable skin which lacks the necessary entries for RasPlex and uses PC-specific strings instead.
For some skins it's also configurable which commands should be displayed, both for the main menu and its side menu.
And in that case you haven't configured those settings properly yet.
Also, "Reboot" is not an option in any settings. The side menu has a command "Restart" just below the command "Shut Down".
Below is a sloppily made photo I took while writing this post, to show you how the side menu should look, when using the original 'Plex' skin in RasPlex 0.5.1
NB: The stuff in the right-hand part of the screen is the 'On Deck' and 'Recently Added' fanouts of my TV shows, because that section was selected in the main menu when I pressed DPad-left to open the side menu.

When I took this photo my RPi2 was running RasPlex 0.5.1 under BerryBoot.
(It's the most convenient way for me to keep multiple RasPlex versions for reference testing, like now.)
Best regards: dlanor