Not sure how much I could elaborate on that, but it’s something that is used in schools to indicate teachers have a no tolerance for certain behaviour (violence, harassment, hate speech etc.), the downside is it sort of oppositly implies that there are unsafe places. Many school environments try to implement no-tolerance policies about bullying but it’s often not effective as individual personalities may differ or people rather turn a blind eye than stand up. It’s a bit naive to think that an entire community can exist without, but I understand the ideal.
I think that safe space label on profiles is a bit more broad term that might resonate and be safer alternative to something LGBT-related. As others have said, being homosexual in a lot of places is unacceptable or punishable, but tolerance can not be defined or punished as easily. It kind of goes along with the idea that having thoughts isn’t necessarily bad, but acting on them is. The word safe space can resonate with LGBT-community members, or even people that have generally been bullied or harassed, or other minorities. It’s not one specific group.
As for creating a community, can’t say that I have an answer as I’ve never seen a community without some type of harassment. If you mean dedicated features it might be as simple membership to groups that aren’t visible publicly, but even then people can find what they are looking for in non-anonymous settings. Since I’ve never seen the solution myself, unfortunately my mind isn’t innovative enough to imagine it. As side-note, I think that’s something that lot of LGBT people grow up with thinking about: no matter where they are and how out and proud they are, there is always going to be times where they have to hide that part of who they are. As a result most get pretty good at code-switching.