You cannot reply to them because that account is a robot. If you want to speak with a member of ATA (the creators of PIMD) about your silence, you need to send a help ticket. You can do this by pressing on the home button, pressing on the cog icon in the upper left, pressing "Help," and then pressing "New ticket". Then you can send your message.
Here's an example of what not to say on your own wall because you don't want to offend any individual who may be stalking your wall.