Rotate Display 180 Degrees

You can use setRotation, but as you noticed it can be slow (there are some 'fast paths' that don't activate when rotated). However the screen itself can rotate, which will be the fastest.

If you paste the following into the IDE:

require("Storage").write(".boot1",`
Bangle.lcdWr(0x36,0xC0);Bangle.lcdWr(0x37,[0,80]);
g.clear();
var _ = BTN1;
global.BTN1=BTN3; global.BTN3=_;
_=BTN4;global.BTN4=BTN5;global.BTN5=_;
delete _;
`);

Then long-press BTN3 to reload, you should now get a flipped screen and replaced left/right swipe areas. swipe direction will still be wrong though, and vertical scrolling or double-buffering will break things.

Still, for most apps it's surprisingly usable