Yawn… that old one. What does it say in The Beating Debt Collectors Guide about this? You have read the guide right? By them saying this to you, you’ve got them over a barrel. Now you want their proof of claim that this is so and you want evidence of their capacity to provide unsolicited legal advice. After you have asked these questions you will find that they go all quite on the subject.
Maybe get your 3rd party to call them up and pressure them on those points… “how are those notices of no legal standing?“, “are you claiming only your notices have legal standing?“, “what is your proof for those points you claim?“.
We are all equal before the law (allegedly) so if their notices are legal then your notices are legal… if your notice are not legal then their notices are not legal. They can’t have it both ways.
It’s just a tactic to make you worry and think that you are making things worse for yourself. Whenever they say anything like that (as if they are helping you) then read it with caution. What do they care if what you are doing has no legal standing? If anything they would keep their mouths shut so as to let you dig a hole for yourself that would allow them to get a judgement against you.
You will nearly always find that the opposite is true to what they say. They say you can’t do this or that, you can bet you can do this or that.