Question about the fallacy of the Self-Sealing Argument

Dear Mr. Bennett. I need your help in the following:

1. Can a performative contradiction be considered an example of a self-sealing argument?

If the answer is yes, then please respond to the following:
a) Is it valid for person A to say the statement "I am dead", even though the very act of proposing it presupposes the actor is alive?

b) Why is it fallacious to say "you can’t argue against the statement I am dead", even though it is a self-defeating argument [internally inconsistent (self-contradictory)]?

If the answer is no, then please respond to the following:
a) How can the self-sealing argument be used in a debate (other than the religious examples you presented)?

2. What do you mean by evidence in this fallacy? Are you referring to statements that can be made by both a priori and a posteriori forms of reasoning?

Key definitions:

Self-Sealing Argument:
An argument or position is self-sealing if and only if no evidence can possibly be brought against it no matter what.

Performative contradiction:
Arises when the propositional content of a statement contradicts the presuppositions of asserting it.

Not sure if I said that the "acting purposely" argument was "self-sealing," but if I did, I meant "self-defeating" (more specifically the rejection of that argument might be self-defeating). Just in case you do mean self-sealing, the two are different enough that it generally wouldn't make sense to say that something such as "you can’t argue against the statement 'I am dead'", is self-sealing. Hope that helps.