I was surprised to see it - I thought "boffin" was good-natured but highly irreverent, like "nerd". But I can't imagine any publication writing the headline, "Computer nerd claims Microsoft's supposed quantum leap does not compute."
To be fair, "boffin" usually implies someone has relevant (usually scientific) expertise, but nerd doesn't. Henry Legg has the relevant credentials to give weight to his claims, he's not just some random basement nerd.
The Register is highly irreverent, as a rule.
It's typical of the Register. They always use the word "boffin" for expert/scientist. It's a british word used to describe a clever person.
"Good natured but highly irreverent" is pretty much The Register's house style.