reverse-withcomments.bf

>+[                       loop (add 1 so the loop executes; keep #0 = 0)
  ,                       take input
  [->+>+<<]               copy into next two cells
  >>                      go to 2nd copy
  [-<<+>>]                move value to original cell; makes "origin" & "copy"
  <----- -----            subtract 10 from copy

  note: copy's value is not relevant; all that matters is that if it is 0
  (aka if the char was a newline) that it will break out of the loop!
  this means that we can overwrite the copy with the next character; allowing
  for the string to be stored neatly on the tape
]

<         go to last inputted cell
[.<]      keep outputting until the 0th cell is reached

reverse.bf

>+[,[->+>+<<]>>[-<<+>>]<----------]<[.<]