There are 2 columns of icons next to each post. The first shows the folder, with the key showing if there are a lot of posts in that thread. But, then there's the second column. Most just show a plain blue folder or piece of paper, or whatever it's supposed to be. But, occasionally there's something else. Sometimes there's the S for the spoiler warning.
Number one - other than Spoiler - what do any of the other items mean. Number two - if one wants to do that, mark a spoiler for instance, how is it done? ?!?