A theoretical question then, if A defames B strictly via Twitter, can A only be sued at his state, in Federal court, or in California (where Twitter is)?
Depends is the right answer. If A defamed B strictly via Twitter, but the judge determined that A specifically directed the tweets at Texas or Texas social media users, then its likely the Court would find specific personal jursidiction (E.g., #TEXAS #THISGOESOUTTOTEXASSHITKICKERS, etc.) and you could sue them in Texas.
But it it's just a tweet or a series of tweet not directed at state-specific users or the state itself, then you would have to sue in A's home state. I do not believe the fact that Twitter is in California would make a difference. It's the state where the defendant (A in your example) resides.
What are the odds that the complain gets amended if ruled against? Why wouldnt the defamation be linked to the tortuous interference?
As to the complaint getting amended, I would say that there is a better than decent chance the Court will grant a motion for leave to file an amended complaint if Meyer files one. The one reason the Court might not grant a motion for leave to amend is pretty nit-picky and very procedural and I haven't put the work needed to figure out what a court should or might do. But here is the reason,
In his memorandum, the Magistrate made the following statement,
There are discrepancies in Meyer’s characterization of his defamation claim against Waid but the Response does not include a request to amend the Complaint.
My short hand for what he is saying is this, "YOU FUCKED UP MEYER. IF YOU HAD ASKED FOR LEAVE TO AMEND, I WOULD HAVE RECOMMENDED THE COURT LET YOU FIX YOUR FUCK UP, BUT YOU DIDN'T ASK, SO FALL ON YOUR SWORD."
So there is a slim possibility the Court will say, "You had a chance to ask for leave to amend your complaint, but didn't. I'm not going to play around and give you another chance." I think the Court would be wrong to do that, but I wouldn't say 100%.
As for why the Tortious Interference claims and the Defamation claims are not linked, it has to do with how Meyer's attorney plead his complaint. The Tortious Interference claims are all based on telephone calls that Waid made to Antartic.
The Defamation claims are all based on things Waid said in his social media accounts. Note, there is no allegation that Waid made statements in Texas, which the Magistrate noted very clearly:
In the Complaint, the allegations are as follows: Through his various social media accounts, Waid intentionally published statements of fact to his followers and the general public regarding Meyer, including falsely stating that Meyer published the first and last names of comic book store employees to encourage his followers to harass and threaten them, as well as characterizing Meyer as a racist, serial harasser of minorities, and as affiliated with white supremacists.
The magistrate then notes,
In his Response to the Motion, Meyer states the claim differently: Waid traveled to Texas and publicly defamed Meyer (a Texas resident) at a Houston comic book convention. Meyer goes on to argue that “Waid repeated the defamatory statement to a Texas audience in Houston. Waid should have every expectation of being haled into a Texas court as a result.” Id. at 14. But as alleged in the Complaint, Waid’s Houston statements are not the basis of Meyer’s alleged defamation claim. Meyer has not cited any authority that supports his argument that a defendant’s later repetition of a defamatory statement to an in-person, forum state audience gives rise to personal jurisdiction when the underlying claim only alleges earlier defamatory social media statements.
It's a very tight pleading. As it turns out, perhaps too tight. If the Court permits, amendment would definitely help. I expect to see a motion for leave to amend from Meyer's attorney.