1. Disable deletion of comments from your journal.
2. Write lj post which is guaranteed to elicit a lot of comments expressing either sympathy, anger, or a political opinion.
3. After dozens of people have responded, change the original post every so slightly in a way that subtly, but definitely, alters the meaning of everyone's comments.
I can't think of an example or a manner in which to do this. However, if anyone has a copy of Alasdair Gray's Five Letters From an Eastern Empire lying around - or a copy of Unlikely Stories, Mostly, which contains that story - I'd suggest a quick read through it. I don't want to give away the plot if you haven't read it, but it's definitely the genesis for this sort of idea.