I know other people that just have LJs just to read Friends-Only posts that never post anything themselves. The simple solution is to let those people know that they should set up just a basic free-account to read your Friends-Only posts and change their bookmarks. If they don't want to do that, then it's their decision to not see those posts. You've given them the option at least. If posting things as "Public" negatively impacts/damages the con then it shouldn't be done. Whether you take my advice is up to you, but I really hope you do. Thanks for listening.