man.vim

function! man#highlight_backspaced_text() abort
  set modifiable
  let b = nvim_get_current_buf()
  while 1
    let pos = searchpos('\%(.\b.\)\+')
    if pos[0] == 0
      break
    endif
    let pos[0] -= 1
    let pos[1] -= 1
    silent keepjumps substitute/\%(.\b.\)\+/\=execute("let match = substitute(submatch(0), '.\\b', '', 'g') | let isUnderline = submatch(0)[0] ==# '_'").match
    if isUnderline
      call nvim_buf_add_highlight(b, -1, 'manUnderline', pos[0], pos[1], pos[1]+len(match))
    else
      call nvim_buf_add_highlight(b, -1, 'manBold', pos[0], pos[1], pos[1]+len(match))
    endif
  endwhile
  set nomodifiable
endfunction