I created an experiment a couple of weeks ago where I pulled the comments from a Gerrit change and added them to the current editor.
Disclaimer, I have never written a vs code plugin before. I just wanted to see how hard it was (it was surprisingly easy). So the code might be a bit rough :)
It's a shame that it's not possible to build plugins on top of other plugins.
Then we could utilize what they did in the github plugin. The gitlens plugin also has a nice way of browsing commits and opening them in a diff editor, just loading review comments in gitlens would take us 95% there.
Martin