edit: I may have understood why.
The domain monocycle.info has been locally redirected to the server I’m working on, which is where my WordPress is installed. I did the redirection via the hosts windows file.
But Discourse doesn’t have this redirection, so I guess it has to read these images URLs by itself before somewhat delivering them on the message, and so it can’t find these image?
Not 100% sure this is the cause, but since my website will be launched in a few days, I’ll figure out when the domain will be globally redirected to my server.
I can be wrong but what I understand here is that images may be loading on a secure site (https) but their links are (http) What I understand from that is the server from where the post is published should be configured to fully support https first.
EDIT: but that doesn’t looks like the case, I visited the site and both WP and Discourse are configured to load over SSL. What needs to be seen is how have you configured Discourse WP plugin.
On the first message they were indeed in http, but I have updated my website shortly after, so as you can see on the second message, they are in https.