It seems obvious, but I'll say it anyway.

[jedusor]

Basic respect and common sense: don't do the comment cross-posting thing on locked entries. Mine or anyone's.

Comments

[hahathor.livejournal.com]

I'd say don't do the cross posting thing at ALL. But yeah, on locked entries.

I suspect this is going to lead to a lot of trimming of LJ flists.

[rubrick.livejournal.com]

The LJ info seems to suggest that cross-posting will only work on public entries, which is certainly the way it should be, but whether it actually works that way I don't know.

[persona.livejournal.com]

That's not how I read it:

Please note that you can choose to have comments posted to protected entries cross-posted to Facebook and/or Twitter, and the text of those comments will appear to all your followers on those sites, but clicking the link will not show the full entry to anyone who does not have access to view it. The cross-posting options will automatically be unchecked when commenting to a Friends Only or Private post, so that no protected comments are sent to Facebook or Twitter by accident.

[rubrick.livejournal.com]

I guess I'm not clear on what a "protected" entry is, as opposed to a Friends Only or Private post, and how these concepts relate to a "locked" post, which is what jedusor is asking about.

[jedusor.livejournal.com]

Locked and protected mean the same thing--not public. That can mean private or Friends Only, but private entries aren't relevant here since no one's going to comment on them.

[rubrick.livejournal.com]

That's what I thought — which at first I thought meant the paragraph persona quoted blatantly contradicted itself. I now think the intended interpretation is that you can choose to make it so that comments posted to your own protected entries can be cross-posted (the first sentence), but that you can't cross-post comments on other people's protected entries unless they have set theirs up that way (the second sentence).

If this is correct, then the warning you started with shouldn't be needed — it shouldn't be possible to cross-post a comment on a locked post unless the originator of the post lets you. But it's far from clear.