Learn English – “Good to hear from you”

All that depends on the context where "I hear you" is used. It is as good as "I see" kind of a remark.

If "I hear you" is used in response before you complete a sentence then may be you are tautologic with respect to the other person.

If it is used after you complete a sentence then it is very much a kind acknowledgement.

When someone says 'he/she is not feeling that good' conveys the message that they are not feeling good up to a certain point/level which they normally do in the same condition.

Certainly they are feeling good but not to that level.

Lets take an example:

A business man makes profit of 25% from his business while in the past he made a profit more than 25%, lets say he made 40% profit in the recent past.

In the situation above, the business man can say: He did not make profit that much.

Hopes this helps.