Should critics refer to what they know about a dancer offstage when commenting on their onstage performance? Have things changed since Croce wrote this, now that blogs and twitter give more people 'informal' types of information on dancers?
Farrell's hip surgery was public knowledge, with descriptions of the ways it limited her physically and in the roles she could do. There was at least one article that described how, because she had a medal shaft down her femur, to which the replacement hip was attached, if she landed on that leg badly, her femur could shatter. Peter Martins commented at the time that he did not want to be responsible for that happening.
In fact, Farrell, like every other dancer, is/was graded on a curve. She wasn't capable of or cast in 10% of what she could do physically in the 60's or 70's, and to an extent before the surgery, where she could be hit or miss. Her movement was more physically conservative. Any dancer who is aging, injured, or returning from injury is compared not only to current dancers, but also the dancer's own past performances. A lot of people found wonder and value in Farrell's late, limited performances, especially those who had followed her career for a long time. A visitor from Europe or a newcomer to ballet might not have seen what the big deal was. The same is true of most great dancers and singers at the end of their careers; few retire at their absolute peak.
And, more generally I suppose, are there cases where knowing more about a dancer and their life has deepened your appreciation of their dancing or, on the other hand, got in the way of your seeing their performance? If YouTube comments are anything to go by (big if!) many people seem to find it difficult to watch Kirkland without reference to her personal story - do we really see more of a dancer's performance if we know it's done under great stress, or do people just end up seeing the stress and not the performance?
I think it depends on the dancer and the viewer. For example, I never think about Kirkland's life unless she looks particularly skeletal; she either dances strongly or she doesn't, but I know others who think of this whenever they see her dance.
As a ballet-goer, I tend to view performances differently if I know a dancer is performing with an injury, or if the company is plagued by injuries. I remember one spring season in the 1980's where there were so many injuries at NYCB that Heather Watts was dancing two-three times a night. If she looked tired at the end of six weeks of doing this, I happily cut her some slack. (Others did not and stayed away.) I also understand that after a long season, there isn't always the option of a replacement, or that a replacement would cause a cavalcade of changes, and dancers do the best they can. (Of course, a critical storm of factors can cause this anytime in the season.) I'm more unforgiving when AD's miscast dancers in advance who I think have never shown near the technical facility needed for a role without working them up to that level in interim steps or who are giving continually declining performances without the artistry necessary to make it an acceptable trade-off. For me this was the difference between Kyra Nichols and Darci Kistler towards the end of their respective careers; I do understand that this is subjective.
A critic, though, has a different role, and context is part of that role, which includes when a dancer has an injury or surgery that greatly changes his or her performance ability. When writing a review, it helps to know if a dancer is injured or couldn't rehearse a few days before a major role because of one, because while it doesn't make the performance any better or worse than it was, it's possible to say that under better circumstances, the dancer is capable of much more, especially when there is one review of one cast, and it's a major role debut.
Opera is so much better about this: I may groan any time there's a pre-curtain announcement asking indulgence for an ailing singer, and my feeling is that if it's bad enough to make an announcement, the cover should sing, but, on the other hand, as a friend of mine wrote to me after the recent San Francisco Opera Ring, which was all kinds of brilliant, "Wow, I've never heard an 'indisposed' Siegfried, or actually any other, sing a long high C in that exposed moment in Act III [of 'Die Gotterdammerung']." So the review might say, "Despite problems here and here, he also sang a long, clear high C, and was strong through most of Act III, and his next two cycles might show him in normal form." (According to reports of cycles 2 and 3, he was terrific in them.)
Also, most opera in North America is cast by opera, even if there is a small pool of comprimarios used regularly. Speight Jenkins at Seattle Opera once said, if the audience really doesn't like a singer, he'll give that singer another chance, but if the audience doesn't like that singer again, he won't re-engage the singer, regardless of how he feels personally. This is less of an option in ballet companies.