I'm not sure I get the problem. If you click on the post title, you get exactly the same as you always did, that is the post and comments. I'm using /. classic with full noscript though...
(Aside: Full noscript here too, though I don't think there's a /. classic any more, since the beta seems to be gone, or at least not actively being promoted).
The problem in part is that many people probably click on that spot due to muscle memory - I have for over a decade. Suddenly that link has been replaced by a button that does something totally different and not universally desirable. For no good reason. The paranoid cynics might think that the placement of the social media button there is deliberate to draw accidental clicks or entice people to share more, precisely because of the aforementioned muscle memory. I'm not paranoid, but I'm becoming a cynic when it comes to this site, so I could believe that. From a user interface perspective, there's no good reason for the share button to go there, replacing "Read More". The latter does belong there, because after reading the summary, that's where your eyes are looking when reading - the next line of text. Other than a mouse click, there's no break of flow in order to 'read more'.
The other problem is also UI and usability related. The "Read More" link was immediately obvious as the place to click if you wanted to ... read more. That's why so many people click there. When the share button replaced it, there were no obvious places to click from a visual perspective.
The post title links to the full story, yes, but there's no visual cue whatsoever that it's a link unless you happen to mouse over it. Once you experimentally click there, you can discover that it shares the same behaviour as the read more link, but experimental clicking is bad UI design.
The same goes for the dark blob that's supposed to be a word balloon, I guess. If you understand the symbolism derived from comics (which many probably do, I'll grant you) you know it means something about talking and dialog, so an intuitive leap would lead the user to think that it's a link to comments, or a link to make a comment. But what if the user doesn't want to comment? That's not the first choice for clicking either. It's of course also not visually a link, so the user has to discover it with the mouse like an old 'find the hotspot pixel' point-and-click adventure game. As it turns out, it also does the same thing as the former "Read More" link, so it's not even a shortcut way to jump to the comments, or make one. AND, it's grouped with a set of icons that take the user to a list of stories by topic. Cue the Sesame Street song: "One of these things is not like the others, One of these things just doesn't belong ...". Once again, bad UI design.
A link with the text "Read More" - immediately graspable and discoverable. Good UI design.
Awkwardly placed hidden links with no obvious purpose that have to be discovered via mouse over - poorly graspable and discoverable. Bad UI design.
*That's* the problem.