use of 'that' and comma

[Azah]

a. How foolish you were that is my pain.
b. How foolish you were, is my pain.

I think both are incorrect. There are no need of that and comma. And I can use '!' after these two sentences.

c. You don't know that how important the matter will/would be for me.

d. How the matter will/would be for me you don't know that.

If use of 'that' is redundent for a and b, is it correct to use 'that' in last two examples?

 

[Tarheel]

Perhaps:

What bothers me is how foolish you were.

 

[Tarheel]

Perhaps:

You don't know how important the matter is to me.

 

[emsr2d2]

a. How foolish you were that is my pain.
b. How foolish you were, is my pain.

I think both are incorrect. There are no need of that and comma. And I can use '!' after these two sentences.

They are both incorrect. Are you asking us whether you can use an exclamation mark or telling us that you can?

c. You don't know that how important the matter will/would be for me.
You don't know how important the matter is for me.

d. How the matter will/would be for me you don't know that.
I have no idea what you're trying to say with this but it is certainly not a grammatical sentence.

If use of 'that' is redundent for a and b, is it correct to use 'that' in last two examples?

See above.

 

[Tarheel]

Azah, you certainly can use an exclamation mark anywhere you like. However, that is different from saying it"s a good idea.