Bcoin was frequently used as a reference along with bitcoin core v0.8.0-v0.11.0 when I felt like double checking consensus functions (among other things).

As an aside, I personally think bitcoin core v0.8.0 is the best version of core if you want to learn bitcoin from it. It's a lot more straightforward than later versions. I personally don't enjoy reading any version beyond v0.11.0.

This is also the reason mako doesn't support taproot yet. That code is very new and isn't present in upstream bcoin. I could try to implement it from the BIPs alone, but I won't know what intricacies are present in the actual bitcoin core code until I actually read it.

[1] https://github.com/bcoin-org/bcoin