I work on a project at a large (although not Google-scale) company building a collaborative RTE.
The short is answer is no, there are very few universal truths about how text editing works. You'll experience differences between combinations of operating systems, input modes (Japanese IME for example), software keyboards on Android, languages (RTL languages) and that's just for text itself.
Then when you are thinking about more complex features simple things like "what happens when I double or triple click on this" are a complete crapshoot.
The short is answer is no, there are very few universal truths about how text editing works. You'll experience differences between combinations of operating systems, input modes (Japanese IME for example), software keyboards on Android, languages (RTL languages) and that's just for text itself.
Then when you are thinking about more complex features simple things like "what happens when I double or triple click on this" are a complete crapshoot.