Common misinformation

"The evil alter"
The evil alter is a harmful stereotype used to portray systems as scary and dangerous, though it's entirely possible for alters to be bad, it's not part of the criteria.
"DID is too rare, why are there so many systems?"
most studies show that DID affects 1-2% of the population, 1% of 8 billion is 80 million, put a good chunk of those people online or create communities in real life and you will find many of them! Also being born with red hair affects about the same amount of people, but I'm sure you've met many of them in your life! It's very possible you've seen and met many systems with or without knowing it. These studies also don't take undiagnosed or osdd systems into account, and it's been proven that DID itself goes undiagnosed quite frequently.
"fictives are rarer then brainmades"
Fictives are a type of introjection that happens when an alter takes on traits of 1 or more fictional characters, introjects are no rarer then brainmades, nor are they more special. Brainmade alters are still somewhat introjects just with less identifiable sources, they aren't as different as you think.
"alters are all different people"
Alter is short for alternate state of identity, alters are simply fractures of one, they aren't literally entirely different people nor are they possessions or hallucinations.
"I'd know if you had DID"
DID is often more covert then overt, with studies showing about maybe only 5-6% of those with DID being overt. DID forms as a coping mechanism, most cases of DID are formed through abuse trauma, it could be incredibly dangerous if a systems abuser found out about their system
"you can't have DID and insert another disorder"
DID is comorbid with ptsd, depression, anxiety disorders, personality disorders, conversion disorder, somatic symptom disorder, eating disorders, substance abuse disorders, obsessive compulsion disorder, sleep disorder, psychological non-epiletic seizures and probably more
"alters can't date"
Alters can have any form of relationship with eachother, inner structure can reflect someone's wants and needs and or trauma, there is no scientific information that says alters cannot date, it's common for familial relationships aswell but you don't see anyone saying you can't have a headmate who is a familial figure.
"you can't be a system as a minor"
I honestly can't believe I have to explain this but the disorder is caused by childhood trauma, children are gonna have it.
"you can't have that many alters"
There is no actual limit, the brain will do whatever it thinks is needed to survive trauma. Jeni haynes had around 2'500 identifiable parts.
"alters can only split from trauma"
Correction: a system can only form from trauma, after the system has been caused, in some situations if the brain is stressed enough it can split new fragments still. This is especially common in polyfragmentation, alters may split for "seemingly no reason" which is usually hidden or underlying stress
"it takes fictives years to form"
It takes alters in general any amount of time to form depending on person, I think this idea also might be thinking of how fragments take time to form a solid sense of self that however still forgets that the alter has still become an alter. Fictive or not, alter formation time is dependent on person.
"fictives from bad media are bad"
Alters do not commonly get to choose their source, it's an involuntary thing most times. An alter is not responsible for what their source or source character did in media, they are not their source.
"You can't remember your trauma and be a system"
Amnesia comes in many different forms, amnesia is a complex thing and someone can experience many different kinds of amnesia that has little to no affect on their past memories