The online count in a hyperlinked server invite should not add invisible people.

Easy as that. I shouldn't be able to see (or guess) which one of my friends are invisible or not based on an an invite.

For example, the server may have 5 people. It shows 5 people online.

Though, in the server member list, it shows that one person is offline. Boom, you now know your friend is online.

Even if it says 4 people online, you have a 50/50 chance of of your target being online, when your target wishes that to be much lower.

Thankfully, this only affects small servers, and requires a lot of setup to exploit, but still, it can cause harm, and fixing it causes no harm.

I can think of a few circumstances where this could be used negatively.

Invisible should be invisible.