"John Doe has left the conversation"

Whenever I close a chat window in my spark client, the use I was chatting with gets a notification that I left the conversation. I would like to disable this, however I cannot find anything in the server or on my client to do this. I swear I remember being able to disable this in a previous version of spark. I currently have Spark 2.8.3.960. Any suggestions? Or do you know of any opensource XMPP client that can send mass chats as well as server messages?

There was never an option to disable these notifications. This feature appeared in 2.7.0, so maybe you were using older version before. There are two feature requests (one for Spark, one for Openfire) regarding this. A few years ago one person reported he will work on this, but he never submitted anything. So, nothing can be done now.

[SPARK-1616] Add an option to disable typing notifications (XEP-0085) in the chat window - IgniteRealtime JIRA

[OF-914] Add an option to suppress Chat State Notifications - IgniteRealtime JIRA