My co-workers tell me it’s either “that’s interesting,” i.e. it drew their attention; or just that they’re looking at something. For example, if I provide a link to a ticket, they’re indicating that they received the link and have clicked or will click it to look at it.
I have also seen one person use it like the Michael Jackson eating popcorn gif when using a messenger that did not support embedded images.
That’s how I would have interpreted it, as well, but I’ve seen it used in situations where that didn’t seem fitting so I asked.