How did Seamus Heaney incorporate Old English poetry elements in this modern translation?
His punctuation copies the half-lines used in Old English poetry.
In Old English poetry, one often used half-lines. This means that each line of poetry was split into two half-lines, and in each of these half-lines there were two strongly stressed words, often with the purpose of giving musicality to the poem. Heaney follows this half-line pattern in his modern translation.