[federicotdn]

Yes, the Gmail web client does this. However my (personal) problem comes more from reading the emacs-devel archives, where the thread view takes the shape of something more like a tree (maybe I'm not configuring something correctly). I was subscribed to emacs-devel at some point (which made reading easier) but it started filling up my account storage so I un-subscribed.

[iLemming]

Use https://yhetil.org/emacs-devel to browse the threads. If you use mu4e or notmuch and often delete some older emails locally, but still want to read the whole thread, you can write some elisp helpers that would find the thread on point (based on email-id) or even download the whole thread.