There seem to be a few different options.
1. Add the error message to FAQ 76; keep info spread out over 76, 157, 148 (Data limits).
2. Create a separate FAQ with that error message in the title.
3. Pull all info into 76; leave some in 148
4. Pull all info into 76; reference FAQ 76 from 148 (Queued posts are limited as described in "blah FAQ")
FAQ 157: What is the "Moderator" option? How does it work?
There are limits on the total number of posts that can be waiting in a community's moderation queue. If a user tries to post to the community after these limits have been reached, he/she will receive an error message stating "Maximum queued posts for this community+poster combination reached," and the entry will not be sent to the moderation queue or to the community. If a user tries to post a second entry while his/her first entry is still in the queue, he/she will receive the same error.
The maintainer will need to approve or reject moderated posts in order for the user to be able to post more entries to the community. The FAQ on LiveJournal's data limitations (http://www.livejournal.com/support/faqbrowse.bml?faqid=148) describes these limits.
FAQ 76: How do I post in a community? should incorporate portions of the above paragraph.
In either case, you should note that some communities may be moderated. This means that any entries you make in the community journal will need to be approved by a moderator.
You are limited to one entry in the moderation queue at any given time. There are also limits on the total number of posts that can be waiting in a community's moderation queue. The FAQ on LiveJournal's data limitations (http://www.livejournal.com/support/faqbrowse.bml?faqid=148) describes these limits. If you try to post to the community after these limits have been reached, you will receive an error message stating "Maximum queued posts for this community+poster combination reached," and the entry will not be sent to the moderation queue or to the community.