Comments/Ratings for a Single Item

This is very similar to Milennium Chess, a commercial variant played on a
15x8 board with only one Rook in the middle of the lineup. I've played it
and found it good, and have communicated with the author (whose name I've
forgotten). He said he had tried 16x8 with two Rooks in the middle but
felt that the two Rooks in the center of the board were too powerful.

Re: Nightriders, it occurs to me you could also create a piece that you
might call an Asterisk, which can move as a Nightrider left and right
(that is, 2 steps along the rank and 1 step along the file, but not vice
versa), or a Rook along the files: so it would have six lines of motion.

My invention Doublechess

http://www.chessvariants.com/large.dir/doubleboard.html

is better than this. I dislike variants with two kings. 
Chess should be single minded. Checkmate one king to win the game.
In Doublechess I replaced the second king with a third queen.
There is an imbalance with the Doublechess game you showed
(I am not quite clear on whether the game you are commenting on
in the link where you say 'for example, this' and show a link on
'this'
but the game shown in that link has an imbalance the bishops are on
the same diagonal with an enemy queen, my Doublechess all the bishops
are on diagonals with enemy bishops) also a game that is almost identical
to that one on a 15 by 8 board with one of the rooks removed and the
center rook being able to castle with either king is a commercially
marketted game called Millenium Chess and is sold by the
United States Chess Federation. It has never been published on this
site  because it is a commercially produced game.)

Anyway my Doublechess is the best 16 by 8 game around,
why try to tinker with perfection?? ;-)

I hadn't seen Doublechess, but it seems to me that Doublechess is not at
all like Doublewide, even though it uses the same size board. Doublewide
has the elegant setup of two normal setups side by side, so simple that I
guessed that it had probably been previously invented. Most important of
all, Doublewide has two Kings, and that's really the most interesting
part.

As for Millennium Chess, it seems to be 15x8 and its rules for the use of
two Kings are strange.

Doublewide is simply double. Mate one King the game is over. Fewest
possible rule changes.

The idea that the two Rooks together are too strong even though they are
opposed by two Rooks together is an odd idea, to say the least.
Cylindrical Chess remains popular even though it has the two Rooks
together.

You must understand also that Doublewide will lead directly to the idea
that 8x8x8 3D Chess should be played with 8 Kings, both to alleviate the
difficulty of checkmating the bare K in the late endgame and also to
shorten the average number of moves per game; and for this reason,
Doublewide is not only interesting in its own right, but it is also a
foundation for further development.

(Doublewide itself is a direct consequence of Twinkie Danger and
Chutes&Ladders, of course.)

The thing is, Doublewide is such a simple idea (I'm still sure that
eventually we'll find an exact precedent), but so interesting (the more I
thought about the game, the more I liked it).

'from army A when on his right-hand board, and army B when on his
left-hand'

Great idea -- but it would also work on an 8x8 board!

What will you name your new game?

'in the case where the pieces are obviously better on one of the boards,
a
mating race.'

Of course, the Kings will take shelter on the side where the pieces are
weaker.

Suppose that the left is Tripunch and the right is Shatranj; with Kings on
the right, you can use the weak Shatranj pieces to shelter them from the
grim Reapers and grimmer Combine. Kings on the left may tie down valuable
pieces in defensive roles.

'Castling your Kings toward the center might'

This might work sometimes, but it should be very fragile. The closer
together the Kings are, the easier it is to get a King fork. However,
putting all eggs in one basket may, as you suggest, permit one to make a
stronger defense with fewer pieces than would be needed to guard the two
widely-separated King sites.

Excellent editor Peter Aronson seems to have found a direct precedent

'in the link where you say 'for example, this'' -- I didn't say it.
Peter did.

The link points to a game that somebody contributed to Zillions and the
game seems to be what I called Doublewide Chess. I didn't notice this at
first since I was reading a comment about double chess and I saw a link to
double chess....