I am having trouble discovering what the icons in the red circle are all about in this:

I assume the "paperclip" indicates that there is an attachment contained somewhere in the thread, but the "thumbs up," "thumbs down," "light bulb" and various emoticons are a bit vague. Most threads don't have those symbols, they just have "pieces of paper" or something. Is this some sort of SMF code, and why isn't it in the legend box?
Noticed it the other day, and I found every instance of the "odd" ones here on Azzgab and pastiched them together into that wonderful image.
Other than JaxTar appears to have the lion's share of them, I cannot make heads nor tails of what metric is at work (if any) for the assignment of these icons to any particular thread.
Axing for a fiend.
TIA