Periods

Doublecheck system prefs > keyboard > text to make sure the box for Add Period with Double Space is not checked.

Even with that System Preference setting unchecked, I find that randomly, though infrequently, I have interjected periods when typing content in Safari in the Apple Support Communities. This has been going on during the entire lifecycle of Big Sur, and also on Monterey with different versions of Safari. I have no idea why it is happening, nor additional corrective measures to prevent it.