As I find this thing about ‘flexibility’ an interesting issue, I will give one more example.
And don’t look at the nonsensical solutions below (nor at the number of letters in each solution).

Clue: I am behind a tree.
[let's say this tree is an 'ash']

ASHIAM: ok? [because the letters IAM are behind ASH]
ASHIM: ok, too? [because "I'm" for "I am" is ok?]
ASHI: wrong [because the letter I *is* behind the ash tree]

But now I look at the clue again: I am behind a tree.
The imagery is very strong here – I see myself hiding behind that tree. And therefore I opt for ASH+I.
Of course, I know, the surface reading (or that what it evokes) and the cryptic construction (based on doing something with symbols) are mixed up now. But see, my intuition tells me that this is reasonable this time because of the visual aspect of what happens in the clue – and so I want to be ‘flexible’.

Apparently, the Guardian’s crossword editor was flexible too in this case, but I also want to add that I think “I should be promoted” would have been a much better option anyway (apart from the discussion above).
Why? Because moving the “I” up is a movement. And I think that an imperative-like “I should be promoted” or “I must be promoted” is a better way to indicate that movement. “I am promoted” feels like something static.
In everything I do intuition plays a big part and this is another example of that – whether one might tune into that or not.

Finally, your Sabre clue did confuse me.
Do you think it is right or not?
When you cut up the clue in separate pieces you’ll get WEED/WITH/DEAD LEAVES RIPPED OFF. I do like the misdirecting use of ‘leaves’, but I am not convinced by the cryptic use of that word in the last part of the clue [I would have preferred 'leaving' but, of course, that would wreck the clue].
So?
Maybe you are so kind to return this ‘Ball of Confusion’.

Many thanks for the blog

Weed with dead leaves ripped off (7)

W/ (D)IDDLED

There were a lot of very well-written clues, like 5ac (with the ‘wrap-up warm’ combination), the superb 13ac in which ‘Former’ and ‘minister’ should be unlinked, 3d,7 (with the neat definition (‘above’)) and 2d.

Not sure though whether ‘Feeling mortified?’ is a good definition for CHAGRIN, even if ‘Feeling’ might be seen as noun.
And the STATIONA/ERY clue was, in our opinion, ambiguous because the first part was described insufficiently. Just ‘needed to write’ for STATIONERY is a bit meagre. We had a feeling that there should have been something between ’3′ and ‘needed’: the word ‘in’ or ‘in + a noun’, for example. It looked like it was edited out.

A lot of the discussion tonight is about 6d, which we thought was clever.
Paul B @41 makes it very clear: it is simply wrong.
Well, I would say, if you follow the crossword rules of Ximenes, yes.
But why should you?
For me, seeing ‘I’ as the person that goes up (with the accompanying ‘am’) is quite defendable. I see me , the person that I am, going up, nót the letter.
Isn’t it time to be a bit more flexible and less rigid, without, btw, handing oneself over to “anything goes”?

We enjoyed this crossword very much.
And unlike you, UY, we found it a bit more than just a pleasant stroll through the park.
He’s a clever setter, Philistine, and we look forward to see more of him in the future.

Just how short a stroll was this UY? 5 mins? 30 mins?

Personally I found it more of a hike. A very enjoyable hike but a hike nonetheless!

Like others who have responded, my way in to the theme came from FLASH and FLESH. Since I already had A . . . E for 3d, AFORE came to mind quickly, and there aren’t a lot of common words with AFORE as the first five letters. That point finally broke the puzzle open for me; I had only about half completed and was thinking this could be another time I couldn’t quite get it.

Thanks, Philistine, for a fun puzzle. I echo the request for more from this setter.