Minor rant about syscovery and people trying to figure out whether they're a system or not, because I've seen like 3 different systems I follow today get the question: "Am I a system?" And it always bugs me--not because the person asking is being rude or offensive by asking, but because there's no answer that feels actually helpful.
So, for the sake of these individuals asking: here is my quick and dirty primer on what to do if you suspect you may be a system.
"How do I reliably know for certain if I'm a system or not?" This is the wrong question, and it doesn't have a definitive answer. There is no single reliable way to know for certain whether you are a system if you are questioning that. You will never get an answer to this question that does not feel at least somewhat inconclusive. Even if you're able to find closure on it for yourself, someone will always have a reason to suspect that you are lying. Self reflection can be questioned. Symptom lists can be misinterpreted. Anecdotal evidence can be disputed. Tests can be inconclusive. Psychiatrists can be wrong or biased. There's no one thing you can point to and say it is the definitive proof that you are or are not a system. You can always have someone read you in bad faith and give you reasons you're wrong or lying. You can always find a way where you function more or less the same as a singlet and take that as a sign that every other sign has been wrong all along.
"Does [x] mean I'm a system/Is [x] a system thing/Is [x] common among systems?" Also the wrong question. Chances are the answer as to whether or not a particular symptom, behavior, or occurrence is common among systems/a sign of being a system is "Yes, but it is also an incredibly common occurrence among non-systems."
Getting really into RP and feeling like one of your OCs. Feeling a very strong connection/like you're seeing yourself when you look at a fictional character. Having arguments with yourself in your head in a way that feels like there's more than one person. Feeling like different aspects of yourself (eg. different gender presentations, different personas, different "modes" based on environment) have their own names, personalities, identities, etc.
All of these things can be signs you're a system. All of these things can be normal occurrences for a non-system. There is no way to be certain. This question will not help you.
"Would treating myself as a system/Would living as a system help me exist more comfortably?" This is the question you need to figure out. Stop trying to figure out whether you fit the "correct" criteria, whether you display the "right" signs. If you're legitimately asking these questions, chances are it's because you've already been thinking what's going on with you may be a plural experience.
And let's be even more realistic: Are you asking these questions because you want to know whether your suspicions are correct? Or are you asking because you think you already know, but you're afraid that if you call your experiences what you feel they are, someone will come out of the woodwork and tell you that you're wrong? Are you asking if you're a system? Or are you asking if you're allowed to be?
Stop trying to determine whether you are allowed to see your brain in a particular way. You are not committing a crime. You are not stealing valor. And realistically, it's not that hard to just... try it.
Sit down with your thoughts. Open your memos app. Ask your thoughts what they want to be called. Try picturing them not as yourself but as other people. Try talking to them. Try giving them space to exist. Start writing things down--when you feel different, what made you feel different, what that "different" feels like. What things you lose track of. What things you forget. The time you lose, the time you don't. It might take a bit to get used to, so do this for a little while. A day, a few days, a couple weeks, however long until you have an answer you're satisfied with.
Do you feel better? Is it easier to think when you can differentiate your own thoughts from everyone else's? Does it feel natural to recognize certain feelings and thoughts as outside influences? Do you feel clearer? Are you more capable of operating and functioning in your day-to-day life when you can recognize the reasons your brain does a particular thing? Then keep doing it. Likely, you are a system. Or maybe you're not--maybe there's something else going on. Maybe you've misinterpreted it, and it's just that the framework of living as multiple people helps you live better for some other reason.
But then, who cares?
Anyone who comes after you with pitchforks for existing in a way that doesn't hurt anyone and helps you to function and live better is an asshole. If you believe yourself to be a system, you are allowed to call yourself a system, regardless of whether or not you find out at some point in the future that hey, actually, you were wrong. You did a thing that helped you. You tried not to hurt people as you did it. You're fine.
Does trying this exercise make you feel lost? Dissociative? Does nothing feel different? Does it feel different in a bad way? Do you find that you function exactly the same or worse than you did before? Does something feel wrong? Then stop doing it. You don't have to prove yourself to anyone. Maybe you're not a system. Or maybe you are, but operating as multiple people isn't actually helpful to you. That's a possibility as well. Maybe that'll change over time, maybe it won't, but either way, regardless of what's actually going on in your head, you deserve to be able to see yourself in a way/operate in such a way that you feel comfortable and can function to the best of your ability.
There are no rules.