NOTATIO

How much do you think may vertical spacing have influenced in all this?
The second beat of the second system can't go up *also* because it would collide with the slur, in addition to all you already said.

I've used a straight brace in the past, didn't like it too much, switched for a brace. Most if not all the editions of that time only had parts, not a score. The autograph from Dotzauer's method, though, uses braces for the cello duets so, perhaps, it is a subconscious tradition! PS: Dotzauer & ...

Now the 6:1 works, but until Dorico was quit and relaunched it would not cope.
Here's another solution, assuming the piano would be right.
Your second solution, which merges yours and mine together, appears to be the neatest one.

Ahah, sorry, it lacked a tiny bit of context!
These are duets for two cellos, and the numbers are fingerings, yes!

Here’s an excerpt from an edition I’ve recently curated. IMG_1886.jpeg The first edition (Breitkopf, 1840) has the centred beam as I’ve decided to keep, while the two revisions that followed (Breitkopf & Litolff, both 1890-1910, not sure of the exact date) forced the beam all in one direction—wh...

I will try again in the morning and post some pictures as well!
Why the composer wrote the F with fermata as an 8th instead of a 16th is a mystery

Good choice, John!
A pain to realise, perhaps, but much more expressive!

To try to make the 16th of the cello align with the 8th of the voice and the following 16th contain everything else before the fermata, I tried to do a 2:1 16ths for the F and a 6:1 16ths for the rest, but Dorico would not let me do it. Upon writing 6:1 16ths it would overflow in the next bar for re...

Nice!
I initially assumed the piano to be right and placed a 2:1 on the first beat, then a 3:2 on the second, which adds more rests to the cello part.
Your solution is definitely more elegant!

How would you write this bar? It's in 3/4 time, and I believe it is clear as is for musicians, but it clearly doesn't fit in 3/4. Screenshot 2024-03-08 at 14.42.34.png If one assumes the piano to be the correct one, the other two parts need to be heavily altered. I will share the option I've chosen—...