Redmine

After a quick look in the bowels of Redmine, I found this :
subject = h(issue.subject)

So yes, it seems to be a Redmine feature.

I guess that you're sending XML and that you escaped your XML data as if it were HTML; there is a difference between HTML and XML escaping, you can do the test at http://www.freeformatter.com/string-escaper.html.

Thanks for the tip, but it didn't work at all :(
For the title I now have "éé" but the description seems good.

As far as I understood, there is no specific process when receiving from the REST API. safe_attributes in the issue model does integrity check, but that's all.

It worked just fine for me:

Edit: (with trunk version)

Processing IssuesController#create to xml (for 10.132.21.139 at 2012-03-01 14:27:35) [POST]
  Parameters: {"issue"=>{"project_id"=>"1", "subject"=>"ééé", "priority_id"=>"6", "description"=>"éàé"}, "controller"=>"issues", "action"=>"create", "format"=>"xml"}