Originally Posted by
WineCountryUA
blocking is where a seat is marked and avoided by agents (GA, RCC, ...) and is no longer done
Asking to be moved to an empty row is a perfectly reasonable request if such exists but there is no guarantee the row will stay empty.
With 85+% load factors domestically, you will rarely see empty rows domestically. While maybe more common internationally, an empty row can not be counted on and will not be blocked.
I survived E+ for 14 hrs with spare seats thanks to an angel who blocked them

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Sometimes seat blocking can be done and has been done

, probably depends on who you know and whether the loads will allow it. I have never asked for seats to be blocked, I asked if they were still empty before I boarded. On another LONG flight, I asked the same question about empty seats and was promptly handed 2 new C BPs for myself and my daughter ^.