Обратная связь была ясной, то есть понятной.

Literally, обратная связь does mean something like reverse connection or feedback loop, but in modern everyday Russian it is the normal expression for feedback.

So in this sentence, обратная связь is best understood as:

• feedback
• response
• comments given in return

It is a fixed phrase, so learners should usually memorize it as one unit: обратная связь = feedback.

Была is the past tense of быть (to be) in the feminine singular form.

That happens because the subject is связь, and связь is:

• feminine
• singular

So the verb agrees with связь:

• связь была = the feedback was

Compare:

• отзыв был полезным — the review was useful
  because отзыв is masculine
• информация была полезной — the information was useful
  because информация is feminine

Because after была in this sentence, the adjectives are being used as predicate adjectives, and Russian often puts this kind of adjective in the instrumental case.

So:

• ясной = instrumental feminine singular of ясная
• понятной = instrumental feminine singular of понятная

That is why both end in -ой here.

Structure:

• обратная связь — subject
• была ясной — was clear
• то есть понятной — that is, understandable

This instrumental pattern is very common after forms of быть:

• Она была счастливой. — She was happy.
• Идея была хорошей. — The idea was good.

Yes. A very natural alternative is:

• Обратная связь была ясна, то есть понятна.

Here ясна and понятна are short-form adjectives.

Both versions are grammatical:

• была ясной, понятной — long-form adjectives in the instrumental
• была ясна, понятна — short-form adjectives

The difference is mostly stylistic:

• the short form often sounds a bit more concise or formal
• the long-form instrumental is also very common and natural

For a learner, the important point is that both can express was clear / was understandable.

They are close in meaning, but not exactly the same.

• ясный = clear, plain, easy to follow
• понятный = understandable, comprehensible

So:

• ясной suggests the feedback was expressed clearly
• понятной emphasizes that it was easy to understand

In this sentence, the speaker first says ясной and then restates it with понятной, almost as a clarification.

То есть means:

• that is
• that is to say
• in other words

It is used to explain, rephrase, or clarify what was just said.

So:

• ясной, то есть понятной = clear, that is, understandable

It tells the listener that the second word explains the first one more precisely.

Because то есть introduces an explanation or restatement, and in Russian it is normally set off with punctuation.

So the comma marks the pause:

• Обратная связь была ясной, то есть понятной.

This is similar to English punctuation in phrases like:

• The feedback was clear, that is, understandable.

Because связь is the noun, and обратная is just the adjective modifying it.

In the phrase:

• обратная связь

the main word is связь (connection / feedback), which is feminine singular.
That is why the rest of the sentence agrees with связь:

• обратная связь была
• ясной
• понятной

The adjective обратная also matches связь in gender, number, and case, but it does not control the sentence.

Here it is singular.

Russian commonly uses обратная связь as a singular noun phrase meaning feedback in a general sense. That is very normal, even though English feedback is often treated as uncountable.

So:

• Обратная связь была полезной. — The feedback was useful.

If you wanted plural in some contexts, Russian often uses other words such as:

• отзывы — reviews / comments
• комментарии — comments

But обратная связь in the singular is the standard expression for feedback as a concept.

Yes, Russian word order is flexible, although the original version is natural and neutral.

For example, you could also say:

• Обратная связь была понятной, то есть ясной.

That changes which adjective comes first, so the emphasis shifts slightly.

You could also move parts around in broader context, but:

• Обратная связь была ясной, то есть понятной.

is a very straightforward and natural way to say it. The order presents ясной first and then explains it with понятной.