There are webmasters who say Blogposts on blog are not good and may reduce value of blog. Is that true ? Why?
It depends on the relevance and quality of the site. If it's a spammy site then yeah it could be harmful to your site.
No Blogposts blog are not harm any way if it's not spam blog it also can harm paid blog if it's spam blog and illegal content it's no problem if the Blogposts blog with quality Google friendly content you will get link juice as well traffic
many big companies are buying links like that. Only thing matters if you are getting it on a related page or not.