I did not attempt to draw a full picture in that comment -- in fact, I could say that I was trying to draw a more complex picture than that historian... As an overall point, you seem to argue against the position that there is an Europe-wide big expansion of the far-right right now, which I did not make. For a more detailed review of my views on this, see my loooong reply to Jeffersonian Democrat.

none of these parties hold significant power

Lega Nord is part of Berlusconi's government, with heavy influence on policy. The current Anders Fogh Rasmussen III cabinet in Denmark survives with outside support from DF (though JakeS is to say what is their influence on current policies). Though not among those making advances in the EP election, BZÖ rules Carynthia, while SNS is part of Slovakia's governing coalition (again with heavy influence, esp. education policy).

mutual quasi-historical claims on large parts of the neighbours territory

Elsewhere, I already argued that the cooperation of a subset of European parties is possible.

As for Mussolini and Hitler, do the final circumstances of cooperation really matter? Such imbalances of power and dependencies may emerge during an eventual future second rise of the European far-right, too.

What should count here is that Hitler 'allowed' the Italianisation of South Tyrol even when the Third Reich was dominant. Also, regarding quasi-historical claims on large parts of the neighbours territory, I referred to (without naming them) the Tyso, Horthy, Szálasi and Antonescu regimes; in Slovakia, Hungary and Romania respectively; which had designs on each others' territories (well, Horthy resp. Szálasi on the territories of the other two while the other two mostly on what they already lost to Hungary in Vienna I + II) while Hitler had designs on the territories of all -- yet they kept the alliance and fought on together on the Eastern Front.

_{*Lunatic*, n.
One whose delusions are out of fashion.}