I sense certain ambiguity here. Thing is that while read lock is sufficient for OPENSSL_LH_stats itself, it effectively depends on write locks at retrieve time. And I fail to see this relation emphasized. Would something along following be more appropriate? "... under a read lock, unless accurate usage statistic is desired. In which case a write lock [for retrieve operations] should be used, for OPENSSL_LH_stats read lock suffices." Idea is to "break" it into two "causality" chains...

This actually emphasizes my point quite vividly. It gives impression that read lock at OPENSSL_LH_stats is sufficient for consistent output. In this case would it be appropriate to omit "or inconsistent" and simply refer to OPENSSL_LH_COMPFUNC(3), and even more specifically to NOTE section?

I'm not exactly happy about "always". Even though we can't deny user looking at inaccurate statistics, we probably shouldn't encourage it. I mean I feel that last sentence effectively does the latter. But on the other hand it might as well happen that I'm the only one who gets that impression. In other words I'd omit "always", would anybody else? I also wonder what effect would "the" have in "For output of the usage statistics". Would it be interpreted rather as "for output of [abovementioned accurate] usage statistics"? If so, it would also be an improvement in my ears...

Both suggestions incorporated and squashed.

typo: retreve -> retrieve

Thanks. Got it correct two lines above :(

Actually, there's a notation, so you could simply have See L<OPENSSL_LH_COMPFUNC(3)/NOTE> for more details ...

... and for HTML output, that'll make for a link to the correct anchor as well.

Fixed, thanks.
I've learned my thing for the day :)