I checked my blog posts in validator and though all results are ok (viaggevolmente.com is whitelisted for summary_large_image card), I am not able to see the card in my tweet timeline.
I am not even sure it should appear automatically after the validation or I should be doing something more. The validator page just reports all checks are ok but it does not add what more I should do or expect to be happening
If you post a new Tweet containing your URL, then the card will show up. On the website it will have a View Summary link in the bottom corner which you click to expand; in Twitter’s own Android and iOS apps it will show inline in the timeline. Cards are not supported in third party Twitter clients.
Note that Cards will not show if your Tweet has images or other media attached, as they will take priority.
actually something weird happened (weird to me)
I had set Twitter setting so that tweet could show in my FB page.
As a result the Twitter card showed in the FB page but not in the tweet stream.
I have already disconnected the FB page from Twitter and I assume this will help.
Yet is the system designed to work like that?
I thought twitter card should appear anyway in my Twitter timeline even if the setting for FB page is activate.
No, there’s no relationship between whether your Twitter account auto-posts to FB - the markup is being used independently by the two platforms. As I said, the Card won’t show if you have images also attached to the Tweet, and you need to hit View Summary to see the card in the web view.