There is no mode binding (`C-h k C-b' returns `backward-char'). I don't know
how to read this (result of showing the keymap in `describe-text-properties'
buffer; at step 1:
(keymap keymap
(3 keymap
(5 . magit-diff-edit-hunk-commit)
(20 . magit-diff-trace-definition))
(67 . magit-commit-add-log)
(38 . magit-do-async-shell-command)
(117 . magit-unstage)
(115 . magit-stage)
(97 . magit-apply)
(remap keymap
(magit-revert-no-commit . magit-reverse)
(magit-delete-thing . magit-discard)
(magit-visit-thing . magit-diff-visit-file))
(24 keymap
(97 . magit-add-change-log-entry)
(53 keymap
(return . magit-diff-visit-file-other-frame))
(52 keymap
(97 . magit-add-change-log-entry-other-window)
(return . magit-diff-visit-file-other-window)))
(C-return . magit-diff-visit-worktree-file)
(10 . magit-diff-visit-worktree-file))
At step 2:
(keymap
(3 keymap
(94 keymap
(108 . magit-smerge-keep-lower)
(98 . magit-smerge-keep-base)
(117 . magit-smerge-keep-upper)
(13 . magit-smerge-keep-current)))
keymap
(3 keymap
(5 . magit-diff-edit-hunk-commit)
(20 . magit-diff-trace-definition))
(67 . magit-commit-add-log)
(38 . magit-do-async-shell-command)
(117 . magit-unstage)
(115 . magit-stage)
(97 . magit-apply)
(remap keymap
(magit-revert-no-commit . magit-reverse)
(magit-delete-thing . magit-discard)
(magit-visit-thing . magit-diff-visit-file))
(24 keymap
(97 . magit-add-change-log-entry)
(53 keymap
(return . magit-diff-visit-file-other-frame))
(52 keymap
(97 . magit-add-change-log-entry-other-window)
(return . magit-diff-visit-file-other-window)))
(C-return . magit-diff-visit-worktree-file)
Paul
(10 . magit-diff-visit-worktree-file))