A moderated comm for fic posting is a step above making someone add you as a friend.
A personal fic journal comm that has locked material, you join, one click reading right then and then if you like, you can unjoin and move on.
On someone's private LJ, you have to friend, wait for them to friend back and hopefully by that time, haven't forgotten you were going to read.
And frankly, if you are going to join a community to post your fics, maybe the moderators of these fandom specific comms need to revisit any policy they have about friends locking entries in that comm.
I still find this atmosphere of paranoia of explicit material must be locked, when the last I saw on LiveJournal applied only to communities, distasteful, especially when it's not necessary.
As I said elsewhere, I understand the reasons why someone would flock a fic on a personal LJ. Doesn't mean I still don't suspect it to be used to pad friends counts and not really out of genuine concern for posting adult content.