Learn Russian: Редактируя текст, я увидел замечание автора. - While editing the text, I saw the author's comment.

This is the core rule for isolating verbal adverbs. The phrase Редактируя текст is a verbal adverb phrase (деепричастный оборот). In Russian, these phrases must always be separated from the main clause by commas, whether they appear at the beginning, middle, or end of the sentence.

How do we know who is doing the editing in Редактируя текст?

The strict rule of verbal adverbs is that they must share the same subject as the main clause. Since the main clause is я увидел (I saw), it is automatically understood that я (I) is also the person doing the editing. If the subject of the main verb wasn't the one editing, using this structure would be a grammatical error.

Why does Редактируя end in -я?

It is an imperfective verbal adverb, meaning it describes an ongoing background action happening at the same time as the main verb. To form it, you take the present-tense stem of the imperfective verb редактировать (редактиру-) and add the suffix -я.

What is the difference between замечание and комментарий for the word comment?

While both mean comment, замечание often implies a critical remark, a correction, or an editorial note on a text. Комментарий is generally a more neutral explanation, a piece of feedback, or a comment on the internet.