Did the legend of the Chelsea Hotel, Manhattan’s premier bohemian inn, ever need cementing? Dylan Thomas, the great Welsh poet and professional drinker, died there in 1953, of alcohol poisoning. Twenty-five years later, Sid killed Nancy there. But for many, the admission by Leonard Cohen, on stage and perhaps not altogether sober, that the woman giving him “head on the unmade bed, while the limousines wait in the street” in the song Chelsea Hotel #2 was none other than Janis Joplin solidified the Chelsea’s place in the popular imagination. Now, the Chelsea is giving back, with a plaque commemorating Cohen’s contribution to the atmosphere. That puts him in the same league as Thomas, Thomas Wolfe and Arthur Miller, and makes the Chelsea into New York’s own Poet’s Corner, just this side of Westminster Abbey.