This has been happening several times over the last couple months, so I just want to make sure everybody understands how this feature works.
When someone sends you a PM here on the forums, you get an email like this:
You have just been sent a personal message by (username) on Furry Writers' Guild Forum.IMPORTANT: Remember, this is just a notification. Please do not reply to this email.
The message they sent you was:
(text of their message)
Reply to this Personal Message here: (link)
If you want to write back to the person, do not reply to that email! If you reply to the email, it currently goes to the FWG Gmail address (in other words, me), and the other person never sees it.
I do treat all misdirected PMs as confidential, of course, but I’d rather not accidentally see other people’s private conversations if it can be avoided. 
Instead of replying to the email, click on the link after “Reply to this Personal Message here”. That will take you directly to the “My Messages” tab here on the forums, where you can write your reply.
I know it’s easy to get mixed up, especially if you’re in a situation where maybe you’re emailing the person sometimes and PMing them here sometimes, and you lose track of what’s where – but please take a second before you reply to double-check whether you’re replying to a personal email from someone or an FWG forum notification, so you’ll know your reply is going where it needs to be.
I’m currently seeing if the reply-to email can be changed to keep this from being a problem in the future, and I’ll update here as soon as I know something for sure.
Thanks!