While there are no rules per se for anything social, these are excellent guidelines that have been recommended. Don't look for any exceptions to the rule. If there are, you will just know. If you don't know, then even if the exception is happening, it simply means you are not ready for it. Keep things as natural and reciprocative as possible. Try to focus on that. If you are getting mixed or unsure signals, then if you've spent enough time waiting feeling it out, then just be direct 1-1 and ask politely. Give like 3-5 days, if a weekend is nearby, usually wait till the Monday after. Sometimes, people don't like to provide closure cause they don't want to hurt your feelings. And some people, they take your response offensively. Not everyone can handle honesty either. Regardless, you are probably the one who has to create the closure in an appropriate way. If you arent' sure, ask around as much as possible before making a big mistake. You might still anyway but at least try not to make a big mistake. You won't regret trying to do "your homework."
It could be something like, for example, that "you can still initiate contact with me, but I can't be FB friends with you anymore because I've never met you once in-person for platonic friendship or a date." If something actually happens, then work with your situation. Certainly don't expect it though. If you have to make the effort to do that, then in a way, you have your answer already :/ Kinda sad, but empowering at the same time.
It could be something like, for example, that "you can still initiate contact with me, but I can't be FB friends with you anymore because I've never met you once in-person for platonic friendship or a date." If something actually happens, then work with your situation. Certainly don't expect it though. If you have to make the effort to do that, then in a way, you have your answer already :/ Kinda sad, but empowering at the same time.