THE HOUSE VOTE against more money for the Senate's new office palace must have rattled windows all over Capitol Hill. It struck at one of Congress's most revered traditions, the genteel concept of "comity" under which each house has let the other run its operations as it liked. At least, that's how it's thought of on the Hill. In fact, what we are talking about is a hallowed conspiracy to promote general extravagance in the shape of such architectural (and financial) monstrosities as the Rayburn Building. Until Thursday, it let the Senate steam ahead with grand designs for still another extravagance - a $135-million edifice bedecked with paneling, high-ceilinged suites, a restaurant and yet another gym.

Especially this summer, the average taxpayer's view of such projects tends to be very clear and very sour. And the voters don't necessarily make fine distinctions between Senate and House empire-building. That's why so many House members balked. They feared, with reason, that the Senate's conspicuous construction might rub off on them.

Neither the battle nor the building has been ended yet. The House rebellion had a certain eve-of-vacation air, as though some members merely wanted a trophy to show to the folks back home. When they reconvene after Labor Day, there will be heavy preassures toward accommodation; after all, if the sniping across the Capitol goes on, the next casualty could well be a fourth building for the House. Meanwhile, the loss of the $54.8 million will not bring the Senate project to an immediate halt. The Capitol architect has around $30 million in the bank to keep the building alive for a while.

Still, despite all those caveats, it's an important vote, as commendable as Sen. John Chafee's attempt to stop the Senate building two weeks ago. At minimum, the expansionists in Congress are being embarrassed and put on the defensive - with a poor show to defend. "Going along" is going out of style. More members are starting to question not just Congress's abysmal architectural taste, but its general extravagance. To all this we say, "Bravo!" and "Encore!"