Lol.. Posting on their walls doesn't always work. But it's the best way to check if their inactive or not. If their status says something like ask me if I'm inactive than I'll farm you, than just leave them alone
I usually check their battle stats. If they are getting 2,000 losses a day and only 5 wins a day. Then I will observe for a 10 days. If I dont see anything to indicate active, I look at walls, gufts... anything to say if active
Posting on the wall can help YOU figure out if someone is inactive, yes. But guess what, you just sent a message to everyone in pimd that the person is inactive too. Congrats cuz now you have to deal with them being dtw all the time. Be smart about it, send a gift instead. It's a quiet Way to determine inactivity. Recently an old farm that I was hitting accepted A gift I sent a long time ago. Although I wasn't hitting I knew others who were so I told em he was active. So don't post on walls, send gifts instead.
If you tell them you're going to farm them cuz you think they're inactive they will It's not an idea, it's the way to do it no questions asked