H
Hydrogen
Guest
Calling yourself "Hydrogen" implies some knowledge of Chemistry, and people versed in the sciences should know the proper writing of H2O and CO2, since the O stands for Oxygen, not for 0xygen or 0 (zero).
It's nitpicking, and I've seen the error before, but it nevertheless bothers me. It's like "your" when you mean "you're", or "too" instead of "to", or "shouldn't of" instead of "shouldn't have". Same thing.
Actually, your correction is incorrect as chemical formulas employ subscripts, and (so far as I know) that typographic control is not available here.