I think he might not of realized you were telling him to watch his language. When I warn someone, I usually will say "<Player>, language please." This helps because then they know who your talking to. Also, "Lang" doesnt make sense if they dont know your talking to them.
Meh, just my 2 cents.
what happened after that last picture you posted spike? the one where he went "wats 5?" did someone finally explain the language rule? instead of just counting out numbers or saying "lang" without getting his attention first.
and if it was explained to him after that picture. did he curse again?
the "holy F***" deserves a warning, and if repeated, a ban. but im extremely hesitant to ban someone for "wtf" and "omfg" when its not directed at someone disrespectfully.