resharper-unity VS UnityCsReference

Best explaination I've found. Use CompareTag instead of explicit string comparison · JetBrains/resharper-unity Wiki (github.com)

I'm a huge fan of the safe navigation operator, but I'd be remiss not to point out that it doesn't work with any references derived from UnityEngine.Object. See for more info: https://github.com/JetBrains/resharper-unity/wiki/Possible-unintended-bypass-of-lifetime-check-of-underlying-Unity-engine-object

FYI it is bad for performance to do null checks on any unity.engine objects: https://github.com/JetBrains/resharper-unity/wiki/Avoid-null-comparisons-against-UnityEngine.Object-subclasses

However null checks for Unity objects are slow compared to standard C# classes, see this link for a brief explanation, there are also many discussions about this on the Unity forum. Not sure though, if that is still true for recent Unity versions.

The fact of the matter is as a primarily C# .NET developer you have all been polluted with bad coding practices from tutorials and partially on Unity's end too. For example non preferred method of using the null-conditional access operator.

I've checked their CS reference code on their Github, both here and here, but I want to dive a little deeper - specifically, I want to know what they're actually doing when determining validity of the Matrix4x4.

Yep, but beyond just decompiling it, the c# layer of code is on GitHub: https://github.com/Unity-Technologies/UnityCsReference

https://github.com/Unity-Technologies/UnityCsReference/blob/master/Runtime/Export/Scripting/UnityEngineObject.bindings.cs (after 2019.1)

The code where the method filtering for the Animation Event Inspector is done, is here (line 190). Is it possible to do something like this? That repository explicitly says:

No reason, you can look at the source of encapsulate

There isn't really a straight forward way to do this, even the QualitySettings editor uses Serialised Properties to get at the data. (Line 343 in QualitySettingsEditor)

This is awesome, thank you! I'm most curious about their Runtime

I think if you want to get into graphics programming you do want to work with OpenGL and similar things, because at the very least you need to understand it all (and decide what parts of engines to use and what to ignore when you get to whole games). It's also worth saying that while you can only publicly get the references in Unity you do get source access at the higher subscription tiers you'd use at a game studio.