I have definitely seen you post parenting advice, mentioning your own child, in a way that sounds like you're an adopter, without clarification that you're not an adopter.
Your experience as an adoptee may be relevant. Your parenting experience just isn't.
This isn't specific to you. Parenting a birth child (no matter the circumstances) is different to parenting an adopted child. I do both. You may think there's enough overlap for you to have stuff to say, but you're a non-adopter telling adopters that. You can argue that if I don't want to listen to non-adopter parenting advice, I should go elsewhere, but I think if adopters are being told to go elsewhere, because I non-adopter cannot cope with the rejection that sometimes adopters don't want advice from non-adopters, then the point has been lost.
I am put off posting on threads when you post your "advice".
Your experience as an adoptee is useful where people want to hear from adoptees. But depending on your age, that may or may not be relevant. Your parenting experience of parenting a birth child is irrelevant to adoption.
But I've made this personal, when I don't mean to. Generally, adopters want parenting advice from adopters, and should be able to get it on the adoption board without having to ask whether posters are adopters themselves. That's why threads don't appear in active, because non-adopters wading in is annoying.