I write much longer comments on my laptop and desktop computers than on my phone. The pains you mention make me write less even when I want to write more. Do not confuse this with “I have made this longer than usual because I have not time to make it shorter.” (Pascal, 1657, though others have said something similar and folklore attributes the idea to many more) - I do often revise long comments on my computer to be shorter, but they are still much longer than what I'd write on my phone. If I spent more time on them on my computer I'd write them even shorter, but still much longer because what I want to say is normally long and complex and a phone just makes the complexity too hard to write.

You won't be surprised I've never got the point of limited space places like twitter...