I'll try and walk the fine line of giving my opinion as both member and mod, which I'm sure will get both members and mods mad at me. :)
I don't agree with moderators getting the last word in with a thread lock in a heated thread they've been heavily participating in, or have a known strong opinion about. I've said as much in the past in the moderator forums. That said, mods are only human. Personally, I have had to learn to take a step back in global warming related threads. I have a strong opinion on the subject (anti AGW) and in the past I had to be very careful regarding locking those threads. I've had members go into PM war mode with me and other moderators after I've locked one of those threads, including demands that I unlock the thread so that they can get the last word in, then I was told I was free to lock it again. Oh, and that's after I've been called a Nazi, among other choice descriptors.
If I feel a thread is getting out of hand that I have a strong opinion on, I now post in the Moderator forum and ask other mods to check the thread to ensure I'm not being biased, and/or will ask them to "take over" that thread so that I basically become a non-mod in it.
As far as locking threads with the last post calling out a poster: Sometimes it is not justified to do so. Other times it is absolutely justified to lock the thread with a hint, or an outright statement related to who got it shut down. I think you guys can generally tell which threads those are -- they usually go quickly downhill only a few posts after the post in question, which is usually outrageous enough to generate one or more "reported post" emails to staff by the membership. And we do use PMs to warn members, especially if they're new, or we think they may simply not have known better, or maybe have had a bad day. You usually see a public statement when we know the poster should have known better.
Which leads me to my final points. We are all, mods and members, different. One person may report a post that doesn't bother another person in the least. Mods have to walk a fine line between addressing the concerns of members who report a post or a thread, and members who think the thread is rolling along just fine. It basically ends up with us not pleasing anyone completely.
Personally, I consider myself a pretty liberal moderator. I'm on this forum pretty much every day, but I usually don't have cause to step in to give warnings in threads or to lock them. This leads some members to think I'm a crummy mod because I let things go too far (and yet others will say I'm too strict). Other mods may be much stricter and lock more threads. This leads some members to think they're crummy mods because they're too strict.
It comes down to the fact that we are all a myriad of personalities and opinions. When APS first started, we were probably a tenth the size we are now, and we were basically just an "offshoot thread" of THR. The small membership was pretty darn like-minded, and Oleg's original vision was that those few of us who were mods at the time would basically just be the maintenance crew and that membership would be largely self-moderated using the "Art's Grandma Rule". It worked pretty well until we started growing and gaining a much more diverse membership that was no longer as like-minded. We had to start actually moderating or else turn into ArfCom.
We still work under the philosophy though, that all members are moderators in their own right who should try to uphold the tenets of Armed POLITE SOCIETY. All members are encouraged to try and save threads they see going South. That doesn't mean jumping in and barking at people -- but if you, for example, see a thread on "best 230gr cast bullet for .45ACP reloading" turn into "1911's are for doodyheads", maybe you can jump in and actually post on a recommended bullet to get the thread back on track.
Mods can't be everywhere at once 24/7, so we HAVE to rely on members to not only treat one another with respect, but also sometimes not be overly thin-skinned. As I like to say, you don't HAVE to post in a thread you don't like -- you can always just drive on. Not getting worked up about a thread and moving to another subject, or just taking a break from the computer, would probably reduce thread locks by 50% and be really beneficial to the blood pressure. It's just the Internet. :)