The issue for me is, they are arranged within 1 item, a "thread", based on "sender". In my case, that sender is a "functional" Id set up on each of several Unix servers to run our app, so each one has a unique email address involving the hostname, and thus would be lumped into separate threads, for example, 4 threads for the Id on each of the 4 servers in a "production" group. I want their messages listed individually by time so I can see what action occurred on which server across the group, and when, just from the messages list.
The subject includes the server, an action, and the TIMESTAMP, so they change all the time (as intended). Thus I can see the startup on server1 failed, or if server2 was shut down unexpectedly, or server3 had an out-of-memory error, etc. I usually delete most such messages after I check them, but not ones I may need to save for "evidence", or just checking out later. Having them lumped together in a thread simply based on where they came from is no help for my purposes, but maybe that would work for you - "YMMV".
Also, I find that I frequently fatfinger several adjacent items in a list on the Android touch screens, so I could lose a message that needs to be saved if it is adjacent to others I do not want inside a thread (another reason I hate capacitive screens and their "twitchiness" vs resistive screens that I can control more precisely with a stylus or fingernail).
Enjoy your threads - they just do not work for me based on 10 years of this kind of work.
UPDATE:
FWIW, I have found that SMS Composer does the job for me.
Also, it occurred to me that it might help to explain my messaging usage pattern in that I have no interest in retaining the computer-generated messages from my work usage more than a few days at most. My personal messages are so few (half dozen a month or so) that threading in that case might be helpful or not, but hardly matters as few as they are - the work usage is what drives my message organizing criteria.
. I personally think it's ludicrous to have threaded messages grouped according to person - I often get messages from unknown senders (business) or organisations whose name I can't always recall. What do I do then? Scroll through 200 SMS messages to find the right one? So why not provide people with both options and let them decide what's best for them? 