By the time the last comment reached the Federal Trade Commission on its staff's proposal to abolish the so-called "Supermarket Specials Rule," the pile included one -- supporting the rule -- from White House consumer affairs adviser Virginia H. Knauer.

The regulation requires food stores to have the items they advertise in stock at or below the price advertised. FTC Chairman James C. Miller III said at a recent breakfast with journalists that most of the 3,600 comments the agency has received are "based on gross misperceptions" of the rule and of its proposed abolition. Repeal would not legalize "bait-and-switch" tactics because FTC rules prohibiting deceptive advertising would still apply, Miller said.

But Knauer, in her comments, cited "convincing evidence that the rule is functioning very well." She recommended that the FTC modify the rule to permit food stores to offer rain checks or comparable goods when sale items run out. This would legitimize common practice, she said.

The White House adviser disputed Miller's view that market forces or other FTC regulations would be as effective as the rule. "The argument that market forces are adequate to reduce stock-outs and mispricing of advertised goods is questionable when one considers the fact that many food stores face little competition in the inner city and that many elderly and low-income people do not have the mobility or flexibility to change stores even when dissatisfied," Knauer said.

When asked, Miller said Knauer was not among those who he thought had misunderstood the rule.

SHOPPING FOR SPACE . . . The free market has interfered with the FTC's efforts to consolidate about 500 employes into one office from five. General Services Administration officials thought they had found the space, and were planning to sign the lease, when the landlord suddenly decided to rent the space to Martin Marietta Corp. instead. Meanwhile, about 150 staff members from the Bureau of Competition face eviction March 31 from 425 13th St. NW. Temporary room has been found in the Bicentennial Building at Sixth and E streets NW, but the agency is worried about finding space for the consolidated office in time to persuade Congress to provide $3.8 million needed to make the move.

INS AND OUTS . . . Karen Stevens Johnston has returned to the FTC to become director of its Office of Congressional Relations. Johnston was deputy director of the office from 1981 to 1983, then left to be press secretary of the Reagan-Bush campaign in North Carolina. She will fill the spot vacated by Bryce L. Harlow, who has moved to the White House congressional relations staff.

Judith A. Pond has been named director of the Office of Public Affairs, replacing Jennefer Hirschberg, who has become Nancy Reagan's press secretary. Pond ran the White House speakers' bureau from 1981 to 1983. Since then, she has worked in the Justice Department's Office of Public Affairs.

JUST KIDDING . . . FTC Commissioner George W. Douglas said last week that he was "really just joshing" when he attributed his forthcoming departure to Washington's weather and his "incompatibility" with Chairman Miller.

Douglas, who took office in December 1982 for a term ending in September 1989, said he intends to step down this September. When he announced his decision in a closed commission meeting, the Texas economist recalled for his colleagues the snowstorm that snarled traffic and made him an hour late to his first meeting.

He reminded the commission that his first motion was to relocate the agency in Austin. He offered the motion the next year, and again this year. "I said I was leaving because of incompatibility with the chairman -- he had voted my motion down three times," said Douglas, an active proponent of deregulation and a close ally of Miller.