Here is some precedent for left handed modes:
https://www.world-today-news.com/so-you-can-activate-the-left-handed-mode-of-facebook-and-telegram/
https://lifehacker.com/enable-androids-secret-right-to-left-layout-if-youre-le-1676267178
https://arxiv.org/pdf/1805.08367.pdf

@JTannerWMF Both of the precedents you cite are using the same system-wide setting that is buried in Developer options on the user's device. No individual apps currently implement their own setting to switch orientation. I imagine this is because it would be more disruptive for a user to go from one app that has right-handed orientation to another app that suddenly has left-handed orientation.

(The third paper you cite advocates for automatic handedness-detection, which would be very cool, but way beyond our scope.)

If we build this option, we would also need to accept some other unintended side effects. Here is how the app would look with a forced RTL orientation in English:

Notice that all the UI elements, including the text, are now justified to the right. I can't speak for left-handed users, but this just seems really unnatural and much more clumsy to digest. I suppose I'm just concerned that a setting to flip the orientation of the app would be too simplistic, and would introduce more annoyances than solve problems.

@Dbrant — just played around with the Gmail app, is it possible to explore this (link to demo video)?

The settings don’t have to be as advanced as in Gmail, it can just be a toggle that says “switch swipe actions” (Read/Unread <-> More).

To make it as accessible and solely rely on swipe gestures, we can go this path (Long press, then tap the contextual top right 'More' menu):

Thanks!

A quick update from my end: After consultation with the design team, I adapted the behavior for gestures to just one gesture (read/unread). Also, a more button per notification icon has been added to the designs to make it 100% accessible. Check out the details here T288065.

Also, some notes from the conversation with @SGautam_WMF, who’s left handed

• SG mentioned that he’s used to the current interaction model in apps, e.g. overflow menu in the app bar, swipe actions or floating action button. He hasn’t noticed or wanted a feature to 'inverse' the interface for left handed usage
• SG mentioned that he’d be in favor of swapping gesture driven interaction models, but he wasn’t using them to date (we looked at Gmail’s swipe customization options together)
• After showing SG some recent designs on Android, he’s used to swipe actions that do the same thing (when swiping left to right or right to left), e.g. mark as read or unread

Thanks for the conversation, Sudhanshu, feel free to add if I missed anything.

Closing since this is now encompassed in T288065.