It’s great to be able to include a personal message when inviting new users to a forum, but I’m suspecting that a significant proportion of those personal messages never get read (and the invite not accepted) because people don’t open the email in the first place. I don’t blame them, given how much quasi-spam we have to sift through every day (e.g. LinkedIn).
So I’m wondering if it might help to allow users to also customize the the emails subject line?
To be clear: the current templates are already doing a great job in signalling relevance to the recipient by putting the inviter’s name in the subject (as well as the topic title, where applicable). But it still looks like a typical quasi-spam email: “X invited you to Y”. It will work if X is very close to you, but if you don’t even know X, it’s probably even a disadvantage to have that name there.
So, concrete suggestion: when the inviter clicks on “Custom message”, there will not only be a message field with a pre-filled text, but also a subject field pre-filled based on the relevant email template.