Social media on-pitch bans are so bullshit I don't even know where to begin.
For a guy like him, a fine would actually even be felt. People will always be stupid and do stupid shit, especially at his age. He was fifteen damn years at the time. Whoever didn't say or do stupid shit at 15 cast the first stone. The FA need to get over themselves and get off their high horses sometime.
If someone proves they're an idiot on social media, then block him/her and move on with your life, just like someone like me who wouldn't touch Twitter even with a forklift and use Facebook only for the chat app. Snitching to the FA do-gooders ain't cool first of all and due to the Streisand effect more people now get to hear about Harvey Elliott doing something stupid when he was 15 then otherwise would, potentially making other kids think what he did was edgy or something. Then again there's no need to ban them from doing their job for that. There's only one "sanctioning body" that should have the ability to ban players for off-field idiocy and that's their own employer - the club, that pays their salary. If the FA had kindly asked the club to take him out for a week, they could've walked out with some moral high ground left intact but instead they resort to this lunacy. The FA are not their employer and they're not the police either.
Had he screamed that towards Kane on the pitch, of course that's a straight red and a ban for misconduct, but this is outside any legitimate FA jurisdiction and should be fully in the hands of the club he plays for.
It's gotten beyond tedious this past decade. FA is supposed to stand for "Football Association" not "Twitter Police". They should get in line, and quickly.