I am using Sharepoint Designer 2013 to modify a Sharepoint 2010 site. I created a workflow starting automatically when an item (both discussions and messages) is changed. However the workflow is not fired upon the deletion of replies. Do you know how to trigger a workflow upon the suppression of a reply? Thanks
Sharepoint OOB workflow does not support trigger on Item deletion. It can be only on addition and Modification.
You will have to leverage Event receivers either Item Deleted or Deleting in your case. That will be C# based code. Since its 2010 site i am assuming its on premise so you can use Sandbox solution which are quite easy and need not have farm admin intervention.
Below is one of the many blogs that talk about event receiver
Thanks Rohit, for your info, the link you shared points to a site which does not seem to exist anymore. However I understood that I would need to create a sandboxed event receiver, preferably using Visual Studio. I found a useful thread here. Thank you very much for pointing me in the right direction!