After I used this button, another mod on the same forum asked how to hide individual posts. I pointed out where it was, but they still didn’t get it.
I wound up having to tell them to use the button that “weirdly enough, has a 
icon” to hide the individual post. It doesn’t say, anywhere, what this actually does.
Could this label be made a bit more informative, like having it say somewhere that it hides the post, or being marked with an icon more informative than the thumbs-up?
I agree. Those texts are descriptions for a dev/coder and admin how buttons are working, not for an user to tell what buttons do.
I don’t use that menu like ever, so I don’t know what Take action does… but if it just hides a post could it be something as Hide post?
Other two options don’t need anykind descriptions. Texts are there just making layout more uniform 
But my bureaucratic side whispers that is not bug, but UX question.
You can change the text of that button for your site by editing the js.flagging.take_action and js.flagging.take_action_options.default.details fields in /admin/customize/site_texts/
Though we’re always open to making changes to descriptions if people think they could be more intuitive. If you land on a good one for your site could you share it here and we can see if it would work for everybody?
Is there a way to change the icon, too?
I believe it may be possible using a custom theme component: