I (well, with help) discovered a small nuance with this feature. I was able to private message someone on my ignore list, after I happened to read a post from them due to quoting. It was an OK message letting them know how something they said made me feel. Didn't give it any thought; however, it turned out that they could not message me back because I had them on my ignore list. Caused a little consternation as they accused me, which was logical based on what was known at the time, of sending them a message and then immediately blocking them. That would be a pretty bad practice, so I don't blame them for being a bit ticked off. Unintended consequence of me working to keep my views clean.