In an answer on another question, @TsuyoshiIto wrote: [U]nlike commas in English, 読点 in Japanese is rarely (if ever) grammatically required. Authors are free to use 読点 wherever they feel that it ...
だが is often attached to the subject/topic of a sentence as follows, with my supposed translation. 近くに住む叔父だが, 最近具合が悪いと聞いている. 'Speaking of my uncle who lives close-by, I've heard lately he's isn't ...