blackblood and armour save

Does the Possessed mutation "blackblood" allow armour saves or not?

As it states nothing explicit, I'd say yes, but how does armour protect from spraying blood? So I'm unsure...

It will allow armour saves unless stated otherwise.

maybe it is strong enough to burn through cloth and tissue but not through hardened leather and metal?

A no armor save ruling would be a house rule. As written it does not say no armor save.

I think I have read somewhere years ago that if nothing is explicitly stated otherwise, armour saves are allowed.

can someone please lead me to that passage (in case there is such a passage at all)...

thanks for your answers, that's what I assumed also....

There is no such passage per se, but there doesn't need to be one. The rules for armour say that if you are wearing armour and take a wound then you get to make an armour save. Because that rule is there you will then only not get a save if the specific thing causing the wound says you will not get a save.