How to use Bluetooth hid

"HID needs to be enabled when turning on the clock"

I don't think this is true now. HID just needs to be enabled when you pair it with your device

Can I assume Android was the primary target this was tested with?

I think it was Windows/Mac OS. However afaik Windows makes it difficult to access the UART connection while using it as a HID device.

Also does it work for anyone with a Linux PC?

I actually tried here and didn't have success.

do you have a commented version of the hid description

I think it's this, but I'm afraid I don't have comments as it came from someone else (https://github.com/jasnell). I believe it is just a modified version of https://github.com/espruino/BangleApps/blob/master/apps/hidkbd/hid-keyboard.js

0x05, 0x01,
      0x09, 0x06,
      0xA1, 0x01,
      0x05, 0x07,
      0x19, 0xe0,
      0x29, 0xe7,
      0x15, 0x00,
      0x25, 0x01,
      0x75, 0x01,
      0x95, 0x08,
      0x81, 0x02,
      0x95, 0x01,
      0x75, 0x08,
      0x81, 0x01,
      0x95, 0x05,
      0x75, 0x01,
      0x05, 0x08,
      0x19, 0x01,
      0x29, 0x05,
      0x91, 0x02,
      0x95, 0x01,
      0x75, 0x03,
      0x91, 0x01,
      0x95, 0x06,
      0x75, 0x08,
      0x15, 0x00,
      0x25, 0x73,
      0x05, 0x07,
      0x19, 0x00,
      0x29, 0x73,
      0x81, 0x00,
      0x09, 0x05,
      0x15, 0x00,
      0x26, 0xFF, 0x00,
      0x75, 0x08,
      0x95, 0x02,
      0xB1, 0x02,
      0xC0

joystick app using the accelerometer

Yes, you could look at using a USB HID report for a mouse/similar: https://www.espruino.com/USB

I'm sure you could get a joystick one working too