I prefer to show the correction in red, as I've seen others do, as it draws attention to the correction. I may also put a little note of explanation either in brackets beside the correction, or underneath the quoted post. I think we are all ready for your next query, Yuri.
(I am studying IT at college, & am currently on HND level, looking at university next year. As a result of this, I may miss the odd piece of English requiring correcting. So, guys, keep up the good work
)