Is providing links to redirecting advertising pages like AdfLy bad ? Those sites pay for clicking the shared link, but are showing advertisements during that. For example that is shorten URL for stackoverflow.com. Can we use it in questions or/and answers ?
Don't do that. If you have a link to share, as part of your otherwise self-contained content, make it a direct link. Don't use URL shorteners and especially not if they lead to advertisements first.
First of all I personally like to be able to see where a link will take me. And I generally won't click on anything that might seem suspicious.
And secondly, you wouldn't want your posts to be flagged for spam, which is not all that unlikely when an advertisement is the first thing someone sees.