Wtf is this?

[DpWm]

Hello!
So there's a flag shaped thing there (in pic)
When I click on it by accident, it makes the whole comment turn a darker colour and then I can't click back on it again to make it look normal.
No idea what this flag thing is meant for. It's a new thing to me by the way, been on the site for years but recently changed phones to a Motorola.

I think that's the bookmark for saving a site

It's for bookmarking a post. Great for long threads so you know where you got up to

But I can't turn it off again! It's annoying.

But ok thanks I suppose I get the idea of it