Is legal action even possible when one's online identity is stolen like that? I can't recall any precedents but it's not an area I know much about.
Yes, it's against California state law (Patrick lives in San Francisco) and is a criminal offense as well as a civil tort. The impersonation must be credible and malicious.
The First Amendment protects practically anything he might say
about me, as unflattering as it may be. But it does not protect him when he pretends to
be me, and in that persona to try to cause harm or defamation to me or others by uttering statements likely to be attributed to me. The law was originally intended to punish cyber bullying, but has been extended to other defamatory and unlawful activity. Since "JayUtah" is a well-enough known moniker for me, and refers to someone who has attached his professional reputation to that identity, then assuming that identity for the purposes of damaging that reputation or falsely endorsing or advocating something, is illegal.
Depending on what I hear back from The Economist web master, I may file a complaint with the San Francisco area prosecutor unless Patrick removes the unlawful posts altogether. Once that is done, the matter is out of my hands. If he finds he has a case, he will prosecute and Mr. Patrick T[redacted]li will stand tall before a judge. The fact that he has changed the offending user name is irrelevant, since the offending content and false identity were allowed to stand for some time, sufficient to be noticed and commented upon by others.