I received a request from a member who prefers to read his e-mails by conversation.  When someone replies to a post in 4.0 and instant e-mail notifications are enabled, the recipient receives an e-mail with the subject: {member name} commented on {topic title} so when viewing e-mail in conversations each mail is separate.  How can I change this to read: There is a new comment on {topic title} which will allow for e-mail conversations to work.

I'm sure it's in ACP --> Customizations --> email but I lack the talent to decipher the HTML and make the change, can anyone help?

Or is it in the language setting?

It's in the language settings, go to Language and click on Translate and search for "commented on" and look at the key to identify the string for email and edit it the way it suits you  

I will give that a shot, thank you.