As far as I'm aware, the proper name of the site was always "Reddit". The logo graphic stylizes it as "reddit", and e.g. Wikipedia points that out for clarity, but official communications use the capital letter.
PhasmaFelis appears to be correct, though. Wikipedia says it’s officially Reddit, and Paul Graham always refers to it as Reddit in old writing. Were you thinking of another source? I understand that you’ve linked to a former staff member’s reddit account, but it just looks like staff members wanted Reddit to be referred to as “reddit” even though that wasn’t the official capitalization of the name.
