Thank you to everyone for these thoughtful and detailed responses. My fears have been broadly dispelled, although some anxienty remains. I probably have more to fear in my current setting directly than through a chain reacting involving my degree.
I have posted some thoughts under the first response and will remain engaged in the discussions above.
But this revision seems to be attributed to a different user than the one who originally posted the question. Am I understanding correctly that this is what happened? If so, is that an acceptable thing to do?
One possibility that's on my mind is that the OP account might be a throw-away, owned by the same person as the account that added the thank-you note, since the question (especially as it was originally phrased) is a bit sensitive. Note that there are no comments from either account on any of the answers, though there are comments from the OP account on the question itself.