Tagged in a post, lost 10 relations?

So a Spacebook friend tagged me in a post, asking if I’d seen the latest VA sim and asking if I’d like to go.

For some reason I got -10 relations for that. What gives?

If you didn’t respond, you probably lost some personal points for that.

Didn’t get a chance to. It just said I was tagged in a post and lost 10 relations.

I liked the post, but only got the +2 for liking something. So I’m down 8 for no apparent reason.

How do you actually ‘respond’ to the posts inviting you to do things?