All thoses links are identical (link to the beginning od the thread).

In the desktop version of the web interface, there's an arrow besides every post, after clicking it, there's a button something like "link", that will be the static link to each post.

(I thought I'm the only one have troubles with Google Groups. Glad to know that I'm not alone! I thought I have opened a thread here mentioning the "static link" trick, but I am not able to find it now. I generally find it difficult to find things here...)