(FORTUNE Magazine) – We recently ran an ''Only in America'' item about various phrases (e.g., ''walk-in closet'') now viewed as verboten in real-estate ads because they might violate federal or state fair-housing legislation (which predicates, inter alia, that folks unable to walk mustn't be made to feel excluded). The item triggered a lot of mail in the ''you-don't-know-the-half-of-it'' vein, so we are getting quite expert on fair housing. One now knows, for example, that the Nexis database incorporates 1,756 news stories wherein ''suit'' or ''lawsuit'' appears within 30 words of ''fair housing,'' also that the enforcers in the federal Department of Housing and Urban Development receive complaints at a rate of about 10,000 per annum. HUD's regs would appear to guarantee lots of litigation. The original 1968 fair-housing law was mainly concerned with discrimination based on race, sex, and religion, and emphasized conciliation efforts anytime HUD got a complaint. The 1988 amendments, which expanded coverage to bar bias against the disabled and folks with kids, place a far greater emphasis on trials in which discriminators get nailed. Definitely needing to be adumbrated at this juncture is the fact that the New York Times, whose editorialists endlessly fret about the weakness of fair-housing enforcement, was hoisted by HUD on its very own petard as a result of running real-estate ads with white models. The paper signed a consent decree last year pledging to cut out advertising ''that conveys, through the use of human models or otherwise, discriminatory messages.'' This brings us to the main reason fair housing is so litigation-prone: Nobody knows exactly what is required. We dopily downloaded a quarter of a million words of HUD fair-housing regulations the other day, thinking that surely these would specify every imaginable way of identifying discriminatory * messages. Not a chance. The regulations are wonderfully precise about such matters as the proper dimensions of equal-housing-opportunity logotypes in space ads of various sizes, but hopelessly vague about which kinds of wording are discriminatory. Manuals abound offering counsel to local realtors. One popular guide is the Fair Housing Advertising Manual, published by the Oregon Newspaper Publishers Association but also widely used in other states. The guide lists words and phrases that are forbidden, merely suspect, or totally copacetic, but its reasoning is often hard to follow. It permits ''great for family'' but forbids any preference for ''couples'' or mention of the dreaded ''married.'' Also to be feared is ''executive,'' which might lead somebody to think you have a white male in mind. It is forbidden to say ''must be employed,'' apparently because some disabled people cannot hold jobs, but okay to tout a nearby golf course -- a distinction that seems especially mysterious in that it is elsewhere rated suspect to mention a country club. ''No drinking'' is no problem but, oddly, ''no drinkers'' is out. One has no way of knowing whether all this is reducing bigotry in America, but it has to be creating godawful information problems for willing renters and rentiers. A point made by one of our correspondents, Professor Gideon Kanner of the Loyola Law School, is that fair-housing regulations also constitute a bit of a problem for free speech. Kanner sent along a clipping of an article he wrote last year, marveling at the fact that Nazis can march in Skokie, Illinois, to promote a belief in genocide, but it may actually be a criminal offense in the U.S. to say ''quiet neighborhood'' in a real estate ad. Right now, the free-speech/fair-housing nexus is onstage in Berkeley. Three residents who have registered dismay over a local housing project designed for the mentally retarded and recovering drug addicts have become the targets of a HUD investigation that could cost them big bucks in fines. HUD has subpoenaed letters and articles written by the three, along with tapes of statements they made at public meetings. There is no contention that they did more than oppose the project, but the investigation, which took seven months, may actually culminate in a complaint that they have violated the Fair Housing Act. A local lawyer has been quoted as stating, ''This has chilled debate in the city of Berkeley.'' Please do not write in to say it's about time.