What is the writing on this sticky note tile? Is it a bullet-point list? Or some kind of poem? Or non-words?

LEGO Tile 1 x 1 with Black Writing (Sticky Note / Post-It) with Groove (25389)
First trace of that piece is in LEGO Olivia's Exploration Car Set 41116. It featured stickied on an astronomy-oriented map. 



Probably a bullet point list, and the second word might be Mars ?. No idea about the first one

It was also released in other sets at around the same time, one of those is Emma Creative Workshop 41115-1



In that case the sticky note is in a girly room/workshop, and it could conceivably be a list of two character names, Ian and Marc, as @V2Blast said in the commands. These sets are part of the Heartlake stuff of LEGO Friends, I don't know if there are two characters with these names.

And, in the end, it's probably left vague deliberately, after all it's LEGO, where we are supposed to create new stuff from their bricks, not be constrained by the sticky note's words. As an examples this sticky notes brick is also used in a LEGO Ideas (Old Fishing Store), where it is on top of the cash register, and it's clearly not used for what's written on the note (Ian, Marc or Mars), just as a generic sticky note.