Wasn't V8 written in a cottage in Denmark? http://www.ft.com/cms/s/0/03775904-177c-11de-8c9d-0000779fd2... I cannot imagine that they would take unreasonable shortcuts.

Well, unreasonable now was probably perfectly reasonable at the time of implementation. Perhaps they even have or had a plan to improve upon it, but given other tasks (ES6, etc.) it hasn't been given much priority.

I mean, why would they fix it with high priority if the engine already has reasonable performance and the benchmarks are happy as well?

Even then, why include comments? Is it to support stuff like multi-line strings as comments hack[1]?

[1]: https://github.com/sindresorhus/multiline