diff --git a/autoload/vimwiki/vars.vim b/autoload/vimwiki/vars.vim
index 7946f68..1a9968f 100644
--- a/autoload/vimwiki/vars.vim
+++ b/autoload/vimwiki/vars.vim
@@ -164,7 +164,7 @@ function! s:populate_global_variables()
   let g:vimwiki_global_vars.rxWikiInclSuffix1 = g:vimwiki_global_vars.rxWikiInclArgs.
         \ g:vimwiki_global_vars.rxWikiInclSuffix
 
-  let g:vimwiki_global_vars.rxTodo = '\C\%(TODO:\|DONE:\|STARTED:\|FIXME:\|FIXED:\|XXX:\)'
+  let g:vimwiki_global_vars.rxTodo = '\C\<\%(TODO\|DONE\|STARTED\|FIXME\|FIXED\|XXX\)\>'
 
   " default colors when headers of different levels are highlighted differently
   " not making it yet another option; needed by ColorScheme autocommand
diff --git a/syntax/vimwiki.vim b/syntax/vimwiki.vim
index 66e3610..9d8ba16 100644
--- a/syntax/vimwiki.vim
+++ b/syntax/vimwiki.vim
@@ -295,7 +295,7 @@ if vimwiki#vars#get_global('valid_html_tags') != ''
   execute 'syntax match VimwikiItalic #\c<i>.\{-}</i># contains=VimwikiHTMLTag'
   execute 'syntax match VimwikiUnderline #\c<u>.\{-}</u># contains=VimwikiHTMLTag'
 
-  execute 'syntax match VimwikiComment /'.vimwiki#vars#get_syntaxlocal('rxComment').'/ contains=@Spell'
+  execute 'syntax match VimwikiComment /'.vimwiki#vars#get_syntaxlocal('rxComment').'/ contains=@Spell,VimwikiTodo'
 endif
 
 " tags
diff --git a/syntax/vimwiki_markdown.vim b/syntax/vimwiki_markdown.vim
index 36e9279..4242f82 100644
--- a/syntax/vimwiki_markdown.vim
+++ b/syntax/vimwiki_markdown.vim
@@ -87,7 +87,7 @@ let s:markdown_syntax.rxPreEnd = '```'
 let s:markdown_syntax.rxMathStart = '\$\$'
 let s:markdown_syntax.rxMathEnd = '\$\$'
 
-let s:markdown_syntax.rxComment = '^\s*%%.*$'
+let s:markdown_syntax.rxComment = '^\s*%%.*$\|<!--[^>]*-->'
 let s:markdown_syntax.rxTags = '\%(^\|\s\)\@<=:\%([^:[:space:]]\+:\)\+\%(\s\|$\)\@='
 
 let s:markdown_syntax.header_search = '^\s*\(#\{1,6}\)\([^#].*\)$'