Single Comment

'Isn't it accepted that in a good variant it is desirable to keep as
close as possible to ortho rules?!'

Accepted by who?  I'm not aware of any chess variant governing authority.

A brief perusal of this site will reveal dozens or even hundreds of
variants more unorthodox than Circular Chess.  

'Yet the Circular Society rules disallow en passant and castling.  
(Why are these differences necessary?'

I think the answer provided by the Society seems perfectly adequate.  I
would not expect a neophyte chess player to write a master level game. 
Nor do I see any reason to scorn simple variants.

'Sorry to jump on this, but is that really a good basis for forming
a variant's rules, basing them on the predjudices of a beginner
player?!'

I think the successes of this variant (its own Society and championships)
go far in establishing that Circular Chess was soundly constructed.  Keep
in mind that the audience for Circular Chess seems to consist largely of
pub patrons, not chess fanatics.  If anything, chess variantists who want
to see there games actually played by a mainstream audience might do well
in emulating Mr. Reynolds' design approach.