Seriously, I don't have that much of a bone to pick in this fight, but I think that there have been some articles published in PV circles recommending expansion joints because:
Seriously neither do I, I simply find it misleading to say PV circuits are somehow more dangerous than other circuits and as such need special care when installing raceways that contain them.
1) PV circuit conduits usually must be run on hot rooftops where the issue is most extreme
This in itself is nothing new at all, this has been done since there was electrical work.
2) There are unique dangers (I'll withdraw 'higher') to PV circuits which argue for above-code standards.
You keep saying vague things like this without ever specifically citing a danger that you see.
3) There has been at least one well-known incident in which the lack of expansion joints was thought to have contributed to major damage.
First there is not type of electrical installation in the world we can't find at least one indecent of failure.
And secondly when I look at figure 2 in the link you sent it says the failure occurred in an expansion joint. That hardly suggests I should start adding more of them.
This thread has gotten crazy, can we just agree that following the NEC and using good installation practices are needed for any power wiring?