This is very important and should be use first before making any post or commenting this help a lot in editing your post and replies.
Where and when did theymos make the law that everyone must first use a notepad to edit their posts before publishing in BTT?
It was just his personal opinion and probably he's applying that to himself.
Well, the writing pad itself as we reply is enough but if you want to be formal and perfect with your grammar then use all of those grammar check that have been mentioned.
And before you publish any post, make sure to check and re-read them. We're in an online forum so whether you're formal with your words or not, the thought and understanding are that counts.