Boosting is allowed?

I had a little convo with blaze(not tf2 blaze) and he gave me some deets about his boosting

Blaze 12:29 AM
i boost full time and look at my hours lol
i play on my main about once a week lol
ConnorLuca 12:29 AM
you have 118 wins if it takes you more than that to boost an account your not a good booster
Blaze 12:29 AM
ive decayed to 4000 3 times this season
LOL
wut
ConnorLuca 12:29 AM
uh huh
Blaze 12:29 AM
uh huh?
lol ask nero
ConnorLuca 12:30 AM
yeh dude
Blaze 12:30 AM
bruh u dont even know
haha
stop acting like a 12 year old you look dumb now
if your sr high is really 4.4 i dont want to hear from u.... i boost full time, to 200 sr higher than ur high lol
http://imgur.com/iPQRl6b

from blizards code of conduct:

Exploiting other players is an equally serious offense. Scamming, account sharing, win-trading, and anything else that may degrade the gaming experience for other players will receive harsh penalties.

that means it is illegal.does blizzard do anything to stop it? no.