Three members of the ESV Bible translation committee are very vocal against the use of inclusive language for human beings when it means using different forms in English than the original language has. That's why the ESV tends to translate 'adelphoi' as "brothers" rather than as "brothers and sisters" or "dear friends" as some of the inclusive language translations are now doing (cf. the NRSV, NLT, TNIV, and CEV). The inclusive language translations tend to avoid using masculine pronouns when the group they refer to includes women or girls, and thus some of the inclusive language translations will use the singular 'they', which is pretty much standard in contemporary English but is not really new to English in recent years anyway, despite the claims of those who have resisted it. It's recognized in the Oxford English Dictionary and the Cambridge Grammar of the English Language.
So it is indeed a great irony that the ESV itself contains an unambiguous example of the singular 'they'. Peter Kirk discovered it, and Rick Mansfield has some further thoughts on it. I agree with their general assessment that this is a problem for a translation that explicitly states in its translation policy that it does not translate in this sort of way. That suggests that someone in the editing process did not notice that a translator had done this, either out of a rushed job or because the editor in question, like the translator in question, is so familiar with the singular 'they' that they did not notice. So I'm in full agreement that this is in itself evidence against the view that the singular 'they' is bad English. I do, however, have some reservations about how we might frame our criticism of the ESV on this. In particular, I think we need to be careful not to treat the Grudem-Poythress-Ryken view as representative of the ESV translation committee in general.
Rick and Peter did not say anything specifically that betrays this sort of attitude (or if they did they must have revised it in response to my comments, since nothing I see in their posts indicates this in any clear way), but it's easy to come away from their posts with the sense that the ESV translators as a whole hold exactly the view these three hold. I have no problem criticizing Grudem, Poythress, and Ryken on this matter. They surely deserve such criticism. Their view on this issue has been so loudly proclaimed and accepted as gospel, and their elevation of it to the level of importance they place it on is way out of proportion with its actual level of importance, given that the disagreement is primarily over whether inclusive language is now the norm in the English language (something that seems so obviously true to me that I don't know how anyone denies it). That is a linguistic debate, and they have made it a doctrinal debate, as if theological issues are at stake (and none are, since people who agree with their theology disagree with them on this). Those who do that deserve much of the criticism directed at them.
But I worry about the way this criticism is directed at the ESV itself. Consider the following analogy. If you discovered that three members of the 9/11 Commission all had the same view, and you started speaking as if that view represented the 9/11 Commission, and it turned out they were some of the most partisan Republicans on the Commission, how would the Democrats on the Commission feel if it turned out this was a viewed not shared by the whole Commission? (Or if you prefer, make it three very partisan Democrats on the Commission, and how would the Republicans feel?) That's what I think we're doing if we take Grudem, Poythress, and Ryken as representative of the translation committee of the ESV. They are some of the most partisan members of that committee on the inclusive language issue.
We know that there are people on the committee who think we threaten crucial theological issues if we translate inclusively. Grudem, Poythress, and Ryken are among them. However, we also know that there are people on the committee who prefer not to translate inclusively but don't have the animus that those three have. Most importantly, we know that there are people on that committee who have no problem at all with inclusive language, who have even been involved with translation projects that use inclusive language. Those three simply do not represent the overall view of the ESV translation committee, and I don't think it's fair to complain about the three most vocal members of the oversight committee on this issue in terms that would include all the others. It may well be that this particular translation committee is stacked a little more in favor of one side, but taking that as the view of the committee as a whole, in a way that sounds as if you're saying the whole committee accepts that view, sounds unfair to me.
As I said, nothing in Rick and Peter's posts entails that they were doing this. Rick limits it to "some of the minds behind the ESV", which I don't find as problematic. I wonder if that suggests that these three had more of a role in initiating the ESV than they did, but it doesn't require that interpretation. Peter more ambiguously speaks of "all we have heard from the ESV team complaining about singular 'they' in TNIV". That could mean what we've heard from the whole ESV team or from the ESV team as a team, or it could mean what we've heard from among the members of the ESV team. The latter wouldn't be so bad, but again I think someone could read it as one of the former two, which I would call inaccurate. I think it's important to distinguish very clearly between the three most vocal members of the translation oversight committee and the ESV translation committee as a whole, especially in this case, where those three members have so vocally defended a view not shared by the whole committee and blown it so out of proportion to its actual significance, winning over far too many people toward the same attitude, probably much to the chagrin of the more moderate people involved with the ESV. I'm quite sure that some of the translators would themselves find this whole incident more amusing than embarassing, but if they get treated as if they're part of the original problem I think they'd probably not find it so amusing.