File locking can be a great annoyance. Most *nix OSs don't bother with it and rely on programmers to create lock files like /tmp/somefileyouhaveopen.lock. On both Linux and Solaris, I have been known to have multiple editor sessions open on the same underlying data files, being careful to refresh before committing changes.
Not OS X. It tries to babysit you just like WinDOS. This means that when you view a file in textedit, you can move it to trash, but you can't empty the trash until you close the textedit session that has the file open. There is probably a workaround in terminal to turn off file locking, but why on earth would you want such a feature as "hair trigger delete?". Take advantage of that extra click involved in closing textedit before deleting the file as an opportunity to recall whether you really need it or not. At the price of storage these days, I have never regretted holding onto files I wasn't sure I needed. I have often regretted deleting things when they were my only copy.
To each his own, but the "feature" you are asking for is not a feature to me. To me it is one less level of safety in holding onto my data. A similar case can be made for "cut and paste". Finder doesn't support it but Pathfinder does. I paid for Pathfinder but rarely use it and even when I do, I rarely use cut and paste. While it may seem like extra handholding about a trivial issue, I rather like that extra click on the way to flushing old data down the toilet. When you consider all the extra clicks and dialogs involved in a Windows environment, this one extra click on the way to deletion seems like a small price to pay for doing things the "Apple way."
This sounds like an opportunity for a third party app "view and nuke". You could browse a bunch files and mark some of them for deletion with one confirmation click at the end. But using textedit and other normal OS X applications in this way locks the files because the OS assumes you are making changes you don't want to lose.
Solaris and Linux are aimed at the workstation market where the programmer is justified saying something like "Shame on you for not saving your work". Since OS X is aimed at average users, I'm very tolerant of Apple's decision to make file locking the default behavior.
