[octo_t]

because browsers in the 1990s were radically different to how they are today. Writing one from scratch lets you learn from past mistakes.

Its immature to start with, but if you have a reference engine (say gecko) and source test data (say the entire internet), you've got some pretty awesome tests already.

I am quite sure the people working on servo have got a lot more experience working with browser engines than most of us, and most of them are contributors to firefox/gecko. I would add that using servo, they manage to find several "bugs" in the new css specification that would have made parallelising CSS layouts much harder (due to servos inherently parallel nature)[1]

A new language that prevents some of the most common security issues via the typesystem will be more secure, whilst not sacrificing the low level performance of higher level language (like Java etc).

[1] - see this comment here: https://news.ycombinator.com/item?id=7484536