I am a Kickstarter backer so my watch is one of the original batch.
A few days ago my battery graphs looked just like those posted by user 150445.
I have a very old laptop with no bluetooth so can't use the web IDE on that. One day I'll get to grips with it on my phone but it doesn't seem to like my browsers of choice, more likely user error. I'll have to try a browser that is more vanilla but I try to avoid Google's spyware as much as I can.
Brave might be worth a try.
Since then I have updated to 90, removed all apps and reinstalled my old favourites,
Since charging on 1st November things have returned to normal and the Bangle is currently showing 90%.
So I'm happy again.
I'm pretty sure that it was one of the apps causing the excessive battery drain.
I haven't a clue what it was so I apologise for this less than helpful post.