I also think it's far more important what the button does than what it says.
For example, on twitter, the "like" button was labled "favorite", which suggests a behaviour akin to a bookmark. But, because the effect was to notify the author of the message it serves as an acknowledgement. And because it also puts your avatar on the message, it serves as an endorsement.

You could remove the name, and just use a meaningless symbol, say, a banana and if it had the intended effect, people would figure that out and use it that way.

So if you wanted a bookmark it should remember that for yourself, but not show an effect on the message, or notify the author.

says @Kodo after asking for emoji reactions

@Kodo I was just thinking that.