A rational proposal to reduce blind FC invite spam
Unfortunately, there isn't a way in game to just auto-decline FC invites while allowing everything else, like party invites and tells.
However, there still are problems with blind FC invites. I think there's a very easy fix, removing the Player Search feature. This is the intro screen.
https://i.imgur.com/1uAO0Ua.jpg
Once you go through that intro screen, and search results come, you can literally send FC invites to everyone without a FC.
https://i.imgur.com/C8EZXuP.jpg
As you can see, it is way too easy for a mass recruiter to send spam blind FC invites by right clicking on characters who don't have a FC.
So there's two fixes. One fix is to get rid of the player search feature. The second idea is to remove "Invite to Company" when right-clicking on a character found using player search.
Lemme hear your ideas.
Edit: A solution I like that someone here suggested is a cooldown on FC invites. The cooldown would end either when the person invited accepts the FC invite, or five minutes, which is how long a FC invite lasts before it expires.