Builtin support for nested comments or a canonical way to handle them

[vmchale]

Currently, I use an approach here, which is as far as I can tell the correct way to implement nested comments.

I'd also like to keep annotations which are kept in nested comments, which I imagine is possible but isn't straightforward to me. Ether a canonical example or builtin support would be wonderful.

Thanks!

[simonmar]

Good idea. Pull requests accepted :)