Yes, this idea strongly related to Editing off for each layer by default. But since that idea has been implemented, I'm not sure that any comments added to that idea will be heard. I think that idea needs to be taken to the next level.
Problem 1: "Make newly added layers editable by default" should be unchecked/disabled by default. Users should "opt-in" to this option.
I just downloaded and installed ArcGIS 2.1 one day after it was released. In previous versions, I was experiencing very significant interface lags when switching to the "List by Editing" pane in the TOC. But this lag now appears to be fixed in 2.1 (thanks, ESRI!). So I proceeded to edit some polygons in a file geodatabase. To double check my edits, I added our county sectors polygon layer, stored in Oracle SDE, so I could review my edits sector by sector. I found a few polygons from the layer that I had been editing (not the newly added sector layer) that needed to be split. So I selected the polygon, used the split tool to make a cut, then selected and deleted the portion of the polygon that needed to be removed. I split and deleted a few nearby polygons, saved my edits and then zoomed out. Two of the sector polygons had been deleted. That was fairly alarming because the sectors are an important reference layer.
I immediately switched to the "List by Editing" pane and saw that the recently added sectors layer was editable. Then I looked at the editing options and saw this:
I'm fairly certain that I've unchecked this option in every previous version of Pro that I have installed, but perhaps I didn't do this in 2.0. Regardless of whether or not this setting carried over from previous versions, I think this option should never be enabled by default. Accidentally deleting two of our important sector polygons is a good example how this setting can be quite dangerous. (Thankfully, I had recently exported the sectors to a file GDB, so I was able to recover the deleted polygons).
Problem 2: Layers from an imported MXD are editable by default
Disabling the setting mentioned above doesn't seem to apply to layers imported from ArcMap MXDs. I made sure that I unchecked the "Make newly added layers editable by default". Then I restarted ArcGIS Pro. Then I imported an MXD into a new map. This is what I saw:
Every map layer was editable by default. As you can see, this map contains some important layers: zoning and parcels. I don't have edit privileges on the parcels, but I do have permission to edit zoning. Accidentally deleting zoning polygons or zoning annotation would be a bad mistake, especially if the deletion had gone unnoticed for a few days. This problem needs to be fixed!
Problem 3: Layers were that editable when an ArcGIS Pro project is saved and closed are editable when the project is re-opened.
I just stumbled upon this problem today. I was editing one layer in a Pro project and then closed it. Then the layer was automatically editable when I re-opened the project an hour later. This could lead to accidental deletions and unintended edits mentioned above.
Proposed Change: Creation an option like "Require all edit sessions to be manually started"
I think every edit session should be started deliberately, intentionally, willfully and knowingly, especially now that Pro can simultaneously edit two or more different workspaces (e.g., file GDB and SDE). I've manually started edit sessions in ArcMap for nearly two decades. Although it was a little bit inconvenient, the ArcMap approach was less dangerous and less error-prone. As long-time ArcMap users transition to editing in Pro, I think they'll assume that no layers will be editable until they explicitly start an edit session. I imagine a significant number of people could also stumble into this pit-fall. These mishaps could be circumvented by adding this suggested option and enabling it by default.