The built in TextEdit seems to fit quite a few of your requirements just fine. Have you tried it out?
Command-shift-t puts it in to plain text mode (instead of rich text) which makes it monospaced, and it has most of the other features you are looking for in that mode.
Requirements (all met):
- Support for UTF-8, UTF-16, Mac OS Roman, Mac Japanese, Windows Latin, and more
- It has full cut/copy/paste support (including for column selection using option-highlight)
- Monospaced (mentioned above, repeated here for completeness)
- Find and replace (command-e uses the selection for find, super handy)
- It has been around for forever, not sure exactly how long, but basically forever
Nice to haves (a few of them):
- A few of those formats are supported (listed above)
- You can select the font and size for plain text in the settings
- I have a 10 MB XML file open in TextEdit right now, no sweat (handles it better than Xcode actually...)
Nice to haves it doesn't have:
- Wrapping - I thought it did, but it doesn't seem to, my bad.
- Line and column numbers - it doesn't display them, but you can jump to a specific line using
Command-l and you can set the width of new windows in preferences to a certain character width, so as long as you don't resize the window it will be the width you want
Prefer to avoid:
- Unfortunately for you it does allow drag and drop editing
Must not have (it has the first two, but they can be disabled):
- It does have support for stylized text, but only in rich text mode, which you can switch out of using the command I mentioned above (and it goes in to plain text mode automatically for code and .txt files-basically anything but .rtf files I believe-so it shouldn't really be a big concern for most editing).
- Save on close - it does save on close, but only if you enable it (and I believe it is off by default) under the General tab of System Preferences. I am 99.99% sure it doesn't have autosave or any other kind of auto disk writing stuff.
- 'Most other features was' a little too vague to answer properly here, sorry. :P
Here is a picture of the settings for turning off saving on close (note that these are global settings for every application on the computer):
So I hope you see that it is actually a pretty good candidate, and it is built right in to macOS! I love it and have used it for many a quick code change (I am more of an IDE guy myself, but sometimes a quick change means for a quick editor).
It may not be exactly what you were looking for but it is quite the handy tool to have built in to the OS. And there are a few preferences you can set to enable or disable features you don't want on a per file basis (in the format menu) or on all new files created (in the preferences window).