为什么what’s the problem？
为什么我不能在别人的小黑板上留言？
why i can’t write down on the other‘s blackborad？

Question

为什么what’s the problem？
为什么我不能在别人的小黑板上留言？
why i can’t write down on the  other‘s blackborad？

Answer

Sometimes you have to be friends with that person. Others won't use it for privacy issues, as scammers & spammers can read them too!