You won't have any problems opening an.Markdown includes no metadata whatsoever, just like plain text.Pages/Word/Excel/Publisher/Scrivener have their own metadata formats.Created in 2004 by John Gruber (open standard).
It lets you style text but still maintains the integrity of a plain text file.It's a way of writing styled plain text (if that makes sense).Markdown is where everything ties together.Taskpaper ($24.99) is where I manage my to-do lists (iOS = Editorial).Editorial ($9.99, Universal) is where I manage/view text files on iOS devices (search built in!).Typora (beta) on the Mac is where everything usually starts.Everything starts with Dropbox - nested files live here, and everything syncs here (saving files).Dropbox + Typora + Editorial + Taskpaper.iCloud also an option to sync on iOS/Mac.Sync with Dropbox is probably your best option - fast and reliable.iOS: Drafts, Editorial, Byword, 1Writer.Mac: Typora, Taskpaper, Byword, TextEdit.No matter what platform you're on, there's plain text support there.Plain text is perfect for preachers because we so often live in text - not so much a need for spreadsheets and formatted materials, but most of our stuff is for internal use and mostly only seen by us. Setup and customization can be time-consuming and difficult.Sync may or may not be instant through various services (looking at you, iCloud).Need for nested file structures in a sync system (such as Dropbox).So nerdy and simple some people don't (or won't) understand it.Limited Styling - some styling through use of Markdown (but can paste easily to other apps).Flexible - can import plain text into anything (Word, Pages, code editors, web forms, Taskpaper).
Editable - edit on the go, no need to PDF anything, make last-minute changes to lessons, sync through Dropbox/GDrive.Robust App Ecosystem - tons of apps for iOS, a few for Android (iText Editors).Future-Proof - will work on anything in the future, almost certainly.Small - takes up a tiny tiny amount of space (1GB = 1000 MB = 1,000,000+ text files).