Is there a link somewhere as to what the little symbols to the left of topics mean? Most just seem to be a little piece of paper with the top left corner folded, but I've seen a few others, including what looks like a cell phone on one of the MTF forum topics.

Just curious.

That is the message Icon.  It can be changed at the top of the topic/reply subject line.  This one is for a standard message.

https://www.susans.org/forums/index.php?action=help;page=index

aka the help page