I have been using SwiftKey on Android for years, switched to iPhone a few days ago. Very unhappy with the ways comma work here. To insert a comma and a space after it, I have to hit the "special symbols" button, then comma, and then the space bar. Alternatively, I have to press and hold the "." key, then move to the comma, then hit space. That is 3 keystrokes, whereas in Android it only took one (you have the comma button on the default keyboard to the left of the space bar, and an empty space is automatically added once you hit it). Likewise, it is also annoying that no space is added after hitting the "." button, however at least this can be fixed by using a double-tap on the space bar to create the dot instead.
I understand SwiftKey is trying to imitate the way the native iOS keyboard works in this regard, but frankly, that setup is just horrible, so please at least give us the option to customize. A comma is a button that is too frequently required not to be on the main keyboard, and in at least 90% of cases, when you type a comma, you want an empty space behind it, so that really should be automatic.