No, I'm not for banning it, but I agree that it can be annoying. I must say that when I do use a phone, I make sure everything is spelled correctly and punctuated correctly. I always use my iPad, and the automated spellcheck can be annoying. But, I usually catch these mistakes. I just wish people on their phones would look over their messages before they sent them. I, too have the message "sent from my iPad" when I email, but, thankfully, not when I'm posting. It's hard to notice them sometimes. Only when I view my sent messages does it show up. Also, I'm sure many people on this site have their phones or iPads/Non-iPads with them throughout the day and check up on Pokebeach. It's easier to reply to a thread or message then and there rather then wait to go home and send a message (many people will forget).
For those curious, you can turn the email message off in settings. For the iPad, go to settings, then Mail, Contacts, and Calendars, then change the signature.