Asking to oppose or support a flag is not a problem, be it a thread or a PM, as long as it doesn't break other rules - like spamming.
As you pointed above, there is a single thread of asking for supporting or opposing flags. That something good as a community. Community should be stand together to save the community member. I don't know what exactly LFC sent to some users but if he had sent PM to influence the flag, not as he said to look over, that's something not good. Anyway, I don't think a respected user like LFC could be spamming other inbox and try to influence them to oppose the flag.
Why not we make a request to share the PM by Bitcoingirl.club, @sidechain? I think you should PM him to share the PM if you think LFC was trying to censor anything here.