You sometimes see unexpected pre blocks if you create an issue by sending an HTML email. Please see the example below.

[Input]

foo

  bar

[Expected]
!{width: 220px; border: 1px solid #ccc;}.expected-result@2x.png!

[Actual]
!{width: 220px; border: 1px solid #ccc;}.actual-result@2x.png!

This can be fixed by stripping preceding whitespaces from each line in the HTML.

diff --git a/lib/redmine/wiki_formatting/html_parser.rb b/lib/redmine/wiki_formatting/html_parser.rb
index 62445ff3b..b3b45f590 100644
--- a/lib/redmine/wiki_formatting/html_parser.rb
+++ b/lib/redmine/wiki_formatting/html_parser.rb
@@ -30,7 +30,7 @@ module Redmine
       }
 
       def self.to_text(html)
-        html = html.gsub(/[\n\r]/, '').squeeze(' ')
+        html = html.gsub(/^\s+/, '').tr("\n\r", '').squeeze(' ')
     
         doc = Loofah.document(html)
         doc.scrub!(WikiTags.new(tags))