I think the article makes a valid point but it can't get past Americanisms like "noon" or "4 p.m." If people were to adapt UTC, those would be 12:00 and 16:00 respectively. And that just reinforces the main point, that the numbers are largely arbitrary -- but descriptions like "after mid-day" (p.m.) aren't.
Americanisms? Noon in French == "midi" and in Spanish == "mediodia". I'm guessing you're British? I'm pretty sure people say that there in the UK, as well.
The sentiment that 24H time is less confusing to express than 12, I do sympathize with.