Server commands available in singleplayer with weird/bad effects

Exactly as the title states, causing bugs like MC-121629. Will continually update with consequences of all server commands. Commands of note are listed:

• /kick: Exits the world and returns the player to the multiplayer menu.
• /ban: Exits the world and returns the player to the multiplayer menu. Does not prevent future access to the world.
• /deop: Appears to deop the player and restricts access to F3+N, but the player can still run commands. Running /op yields that the player is "already an operator." Access to F3+N is regranted upon a reload Thanks to SirBenet.
• /list: Prints the player alone as expected. (this may be WAI, as it has no reason to be limited to multiplayer)
• /save-all: Saves the game as expected.
• /setidletimeout: Doesn't appear to do anything (I don't think ops get kicked anyway).
• /stop: Exits the world and returns the player to the multiplayer menu (a la MC-45602).