diff --git a/README.markdown b/README.markdown
index 297ab48..b6d1780 100644
--- a/README.markdown
+++ b/README.markdown
@@ -122,20 +122,23 @@ to set the behavior for the current buffer:
 
 _This ‘autoformat’ feature affects *HardPencil* mode only._
 
-When in *HardPencil* mode, Vim’s autoformat feature will be enabled by
-default while in Insert mode and can offer many of the same benefits as
-soft line wrap. But autoformat will cause havoc when editing anything but
-paragraphs of words, such as a code block or table. In these cases you
-will need to disable it, at least temporarily, via a command:
+When you are inserting text in *HardPencil* mode, Vim’s autoformat feature
+will be enabled by default and can offer many of the same benefits as soft
+line wrap.
+
+_Pencil_ will disable autoformat if inside a code block. If it doesn’t, or
+in other cases where you need to disable autoformat, you can do so with
+a command:
 
 * `AutoPencil` - enables autoformat
 * `ManualPencil` - disables autoformat
 * `ShiftPencil` - toggle to enable if disabled, etc.
 
-Or optionally map the toggle to a key in your `.vimrc`:
+Or optionally map the toggle command to a key of your choice in your
+`.vimrc`:
 
 ```vim
-nnoremap <silent> <leader>pp :ShiftPencil<cr>
+nnoremap <silent> <leader>p :ShiftPencil<cr>
 ```
 
 To set the default behavior, add to your `.vimrc`:
@@ -157,6 +160,9 @@ augroup END
 ...where by default, files of type `text` will use hard line endings, but
 with autoformat disabled.
 
+Advanced users will want to check out `g:pencil#autoformat_exclude` to set
+highlight groups for which autoformat will not be enabled.
+
 ### Manual formatting
 
 Note that you need not rely on autoformat exclusively and can manually
diff --git a/autoload/pencil.vim b/autoload/pencil.vim
index 766d7d0..a140982 100644
--- a/autoload/pencil.vim
+++ b/autoload/pencil.vim
@@ -53,6 +53,27 @@ fun! s:imap(preserve_completion, key, icmd)
   en
 endf
 
+fun! s:enable_autoformat(mode)
+  " mode=1  InsertEnter
+  " mode=0  InsertLeave
+  if a:mode
+    " don't enable autoformat if in a code block (or table)
+    let l:okay_to_enable = 1
+    for l:sid in synstack(line('.'), col('.'))
+      if match(synIDattr(l:sid, 'name'),
+             \ g:pencil#autoformat_exclude_re) == -1
+        let l:okay_to_enable = 0
+        break
+      en
+    endfo
+    if l:okay_to_enable
+      set formatoptions+=a
+    en
+  el
+    set formatoptions-=a
+  en
+endf
+
 fun! pencil#setAutoFormat(mode)
   " 1=auto, 0=manual, -1=toggle
   if !exists('b:last_autoformat')
@@ -61,8 +82,8 @@ fun! pencil#setAutoFormat(mode)
   let b:last_autoformat = a:mode == -1 ? !b:last_autoformat : a:mode
   if b:last_autoformat
     aug pencil_autoformat
-      au InsertEnter <buffer> set formatoptions+=a
-      au InsertLeave <buffer> set formatoptions-=a
+      au InsertEnter <buffer> call s:enable_autoformat(1)
+      au InsertLeave <buffer> call s:enable_autoformat(0)
     aug END
   el
     sil! au! pencil_autoformat * <buffer>
diff --git a/plugin/pencil.vim b/plugin/pencil.vim
index c678db0..0826374 100644
--- a/plugin/pencil.vim
+++ b/plugin/pencil.vim
@@ -30,6 +30,20 @@ if !exists('g:pencil#autoformat')
   let g:pencil#autoformat = 1
 en
 
+if !exists('g:pencil#autoformat_exclude')
+  " by default, pencil does NOT start autoformat if inside any of
+  " the following syntax groups
+  let g:pencil#autoformat_exclude = [
+        \ 'markdownCode',
+        \ 'markdownHighlight[A-Za-z0-9]+',
+        \ 'mkdCode',
+        \ 'mkdIndentCode',
+        \ 'txtCode',
+        \ ]
+en
+let g:pencil#autoformat_exclude_re =
+  \ '(' . join(g:pencil#autoformat_exclude, '|') . ')'
+
 if !exists('g:pencil#joinspaces')
   " by default, only one space after full stop (.)
   let g:pencil#joinspaces = 0