Android 9 Pie users don't know how good they have it. Android Q will not allow users to swipe to the left or to the right to dismiss a notification. In the next build of Android, swiping to the right is the only way to rid yourself of a notification; swiping to the left reveals a button allowing users to snooze a notification, or block it. In Android 9 Pie, you can swipe in either direction to remove a notification while a slower swipe will reveal the aforementioned snooze and block buttons.
According to a Google Issue Tracker post (via XDA), a future Android release will feature a new setting that will allow users to choose the direction they want to swipe to dismiss a notification. This post comes from a Google email address, which means it most likely is someone who would know.But there is good news for those who are ambidextrous when it comes to their swipes.
Now, we need to figure out what is meant when Google says that the aforementioned settings will appear "in (a) future Android release." That could mean anything from the next Android Q beta to the final release of Android Z, and beyond. However, considering the angst that limiting the swipe direction needed to remove a notification has caused those who installed the Android Q beta (just peruse the issue tracker to see the complaints), we would expect the new settings to be available by the time Android Q has a name, and is rolled out to the very few Android users who will be able to install it this year.
The choices allowed by the new settings could include the ability to dismiss a notification by swiping left, the ability to dismiss a notification by swiping right, and an option to allow an Android user to dismiss a notification by swiping in either direction.