I let em do as they do
As far as the map or the players making a game crappy, it goes both ways in my opinion, I've been in both extremes.
Very rarely do I use map protection, unless it's a mellee map that I like, and don't want to see altered.
Why I don't protect UMS?
I learned most triggers, and editor tricks through trial and error, as well as endless hours of surfing through online tutorials, and asking questions.
When I set up a trigger, I usually label it's action in the comments trigger, for my benefit as well as an aspiring map maker.
As far as someone making changes.....
I have nothing against a few modifications to unit hit points, power settings, moving a location over a bit, etc...
Sometimes a map needs tweaks, that only continuous playing can find.
I guess the only thing that truly erks me is when the map gets a cosmetic overhaul to the text areas, and the name is changed so some lameoid gets all the credit for the map, that is not deserved.
Aside from map protection, there are a few ways that I have found to keep credit for a map, but those secrets will remain mine.
As an example, I went to a clan tryout on a fluke.
The tester/leader was going on about how good their testing map was, I went along for the download if anything else.
It was me, him, and 3 of his newest recruits, against his "Comp From Hell" as he put it.
A few minutes into the game, I recognized it as one of my old maps, with a few changes.
Of course he wouldn't admit to it, even after I had him first look at the Mission Objectives that he didn't change, and a few other labels that he also didn't know about till then.
He accused me of hacking the game, so on and so on, and left.
I then educated his minions a little on map settings and triggers, and where to find my name in the map, before the game ended.
About a week later I got an email from one of the players, because they did look in the map.
It would seem their clan disolved, because of lack of respect from the members.
Oh well stuff happens.
And I got way off track......
If your making maps, disect as many as possible to see what makes em work, take notes, and experiment.
You never know what you may learn.
If it has an email address in it, send a note to the maker, praise or dislike should be welcomed, include comments and suggestions.
But if you make changes, please leave credit as credit is due, you can always add yourself as "Edited By XXXX", I am sure that you would expect the same respect from others.