Distribution of lengths of posts initiating discussion thread. Distribution of the length of first messages in discussion threads for the BBC data. This distribution is important because the first messages are free from possible effects of adjusting the length of comments to previous posts. Gray circles show, for comparison, distribution of all messages in the forum (Figure 1). The initial comments show similar distribution form, but with higher average of 506 bytes and maximum of the PDF at 160 bytes. This is most likely due to the fact that initial comments carry more information and are less likely to consist of short agreement/disagreement/thanks expressions found later in the discussion threads.