I mistakenly flagged [this](http://askubuntu.com/a/599145/380067) answer as spam. The flag was rejected. At first I tought the reason was that in first place the answer, on-topic or not, didn't refer to any paid software, but just to a bash script released under Public Domain license. But after a second look the answer even looked on-topic. So indeed the answer didn't qualify as spam, and that was my mistake. But it's unclear to me when exactly an explicitly self-promoting answer about free software qualifies as such. For some reason, people spam-promote free software as well: [link for those who can see deleted questions](http://askubuntu.com/questions/600123/http-sourceforge-net-projects-freepdftojpgconverter) and [link for those who can't](http://webcache.googleusercontent.com/search?q=cache:yyMumd7qGQoJ:askubuntu.com/questions/600123/http-sourceforge-net-projects-freepdftojpgconverter+&cd=1&hl=it&ct=clnk&gl=it), and to be honest it's unclear to me why this happens. Now the linked question wasn't a question in first place, so there's no concern about whether it should have been deleted or not. But since similiar even tough not-so-explicit things might happen even in answers, this is something I feel I should be ready to handle, since such answers do not make up a high quality post. 

So where do I draw the line and why? Should I limit myself to downvote the answer when it's not a good answer or should i flag it when it's too explicitly self-promoting?