In this case, yes. PJ being a woman is very well known and it irks me when people automatically assume that anybody that runs a thing as successful as groklaw has to be a guy without checking. If you don't know use a gender neutral word or check, it's simple.
It's not purity in language, it is paying basic respect to a person who is named several times in full in this thread.
I think you're brilliant, but I don't know if you are right here. PJ is a private person, kept her name out of the blog for a long while, and I've never seen her make an issue of her sex. This error is made frequently in the Groklaw comments, and I haven't seen her correcting them. While disputable, it's not clear to me that it's more respectful to correct an irrelevant factual error than to follow the authors lead.
The "basic respect" part is tricky. While getting this correct may imply more respect, it also reinforces the idea that the difference is relevant. For example, if she was identified as "Miss Jones" and you happened to know that she was married, does it merit a correction to point out that she is actually "Mrs. Jones" to show proper respect to her status as a married woman?
Hofstadter skewers this in one of this examples: "Ble conveniently sidesteps the fact that there is a tradition in our society of calling unemployed blacks 'Niss' and employed blacks 'Nrs.' Most blacks --- in fact, the vast majority ---prefer it that way. They want the world to know what their employment status is, and for good reason. Unemployed blacks want prospective employers to know they are available, without having to ask embarrassing questions. Likewise, employed blacks are proud of having found a job, and wish to let the world know they are employed."
I don't have an answer, but thought you might enjoy thinking about the issue in the context of Hofstadter's article.
"They" generally works, it's just not commonly used and so sounds a little odd. Try using "they" instead of instead of "he" and "her" for a few minutes to see. It works.
It's not purity in language, it is paying basic respect to a person who is named several times in full in this thread.