Simplenote and autocapitalization
When creating a list (with leading dashes or a checklist), Padkeys autocapitalization causes every word to be capitalized, not just the first. This makes autocap unusable in these situations. This does not happen with the Apple keyboard (iOS 12.3.1). It does not happen with the Apple Notes app, using either keyboard. The Simplenote app must be sending a message that is being misinterpreted by Padkeys.

> ONLY the system keyboard
> capitalizes only the first word.
> Gboard (Google) behaves like
> PadKeys, while SwiftKey (Microsoft)
> stays in lowercase always even at
> the beginning of a list item. It might
> be the app itself is doing something
> nonstandard.
…
And I can confirm that SimpleNote itself is behaving buggily here. When you first tap the checklist button, it sends a “SentenceCapitalization” message. If you then create a second bullet by entering something and hitting enter, it then sends a “WordCapitalization”. PadKeys and Gboard are responding correctly. SwiftKey doesn’t work without full access, but if you grant it, it behaves the same way. The system keyboard may be listening to some other API that third-party keyboards cannot access.
I suggest to report the problem to SimpleNote and ask them to test using Gboard or Padkeys. (I cannot myself find a link inside their app to report problems.)