P: Please let us make "destructive" changes to our images

Would be nice to have 'Has Adjustments' as a Filter option, but the Smart Collection method works just fine. The sorting order solution should suffice also.

Put the images in Library module's  Grid View. At the bottom of the grid should be a toolbar. If it isn't there press [ T ] to reveal it.  Set the Sort Order to Edit Count or Edit Time - whichever is appropriate.  That will group all your edited images into a bundle. 

You can also use a Smart Collection to find Develop>Has Adjustments. 

So I get back from an outing and put a new collection of images on my computer and go through and make various edits, working on multiple images at the same time. Is there an easy way to know which images were edited so that I can export them?

you do get a "quality" level for savings. But a reduction in quality occurs even if the file size remains the same. this has to do with the quantization errors used in the jpeg compression.  You can get reduce quality with same file size.

When saving JPEG I'd like to see a dialog that estimates the percentage of loss for each overwrite. Something like "Warning: overwriting this JPEG will result in a 20% loss of quality, reducing the file size from 3.1MB to 2.5". We all know that JPEG is lossy but having the amount quantified will help us understand the significance. Especially if we feel we need to save periodically to avoid losing work.

Yes, I use Photoshop adjustment layers, filters, etc often when I'm working on an image.  Non-destructive editing is great.  But I also like the option of saving a jpeg instead of the psd file.  I'm highly in favor of non-destructive editing, but I'd like the option to not use it in certain circumstances in LR.  Now I often go from LR directly to PS applying edits to a copy, do something like add a bit of text (a feature mysteriously missing from LR), save a jpeg, return to LR and synchronize folders to get it into LR.   This is only clumsily reversible even if saved as a psd file.   Sorry for a bit of a rant on the awkward interface between LR and PS.  Appreciate the constructive suggestion about using PS non-destructively.

Photoshop does not destructively edit the raw file either. It creates an RGB copy and you could not even overwrite the raw file with that if you wanted to.

Prattle on about deleting raw files if you wish, but do you actually understand that plenty of people do use Photoshop as non-destructively as possible? eg using adjustment layers rather than adjusting an image layer, or applying filters to smart object layers. It's just good practice. 

I would speculate that the future is to keep that den of sin photoshop as a desktop program due to local storage and compute requirements and move more of LR features into the cloud based (non-classic) version over the next year or so.

Ha, ha.  I love it - LR immorally allowing destruction of RAW files.   But  I actually am interested in why there is no similar outrage about Photoshop's destructive editing.  Is it just that it's an old, legacy-hindered (immoral?) piece of software than can't be changed for practical reasons?   Or would the LR non-destructionists like Photoshop to be non-destructive too?

I don't know the future roadmap for LR - do they plan to add more and more editing to LR to eliminate the need for Photoshop?