ExecCommand works incorrectly in Chrome 60 after removing node from selection range
This is likely just a bug in Chrome, but note that per the spec (https://w3c.github.io/editing/execCommand.html) execCommand is in draft and expected to stay there. It's supported, but may not be supported in exactly the same way in every browser. Without a solid specification to follow, implementation is likely to vary, even across browser versions and especially from one browser to another.
Long term, you will likely have more success using implementations that make use of better-defined standards (a challenge, to be sure!) since they're less of a moving target!