P: Ability to sync Lightroom Classic keywords with the Lightroom Ecosystem

We can understand the logic. One is for standalone, the other is for cloud.
But how the hell because that if we want the cloud, we need to leave all what perfectly make Lightroom functionalities be Lightroom.
I think LR CC is now a 24 month old program development and such basic feature are not implemented!
They have to hire some Indians cheap and competent team and we will have all this feature in months.

Sorry Uk is not my mother tongue, hope it will be understandable

The problem is because of a deficient web site (almost for human being),  we most of the time discover such limitation very often when the workflow is so much engaged it is complex to rewind.

And bye the way, why not let people how does not use hierarchical keyword full sync.

Thy way we could use the very expensive combo LR Classic + LR CC + 1TB to compensate the very weak LR CC which is near unusable alone to manage photo but edit

From what I understand, it is deliberate for a technical reason. Lightroom Classic has hierarchical keywords, meaning you can have the same keyword appear in more than one hierarchy. Take 'Los Angeles' for example. Most people would only think about the city in California, but there are many cities with that name around the world. That is where syncing becomes a big mess. When the keyword 'Los Angeles' comes in, how is Lightroom to know which one it is? This is also why Lightroom CC does have keywords, but not hierarchical.

Of course it should be possible to find a solution for this, but apparently that took so much work that they decided not to do it. Furthermore, Lightroom Classic is not meant to be part of Lightroom CC in the first place. Its syncing capabilities are more or less left-overs from the time that Lightroom Mobile existed but Lightroom CC did not. I'm sure that now that Lightroom CC for the desktop exists, Adobe would rather terminate any syncing in Lightroom Classic than enhance it.

When I read those really interesting comment, I find crazy Adobe does not takes in account our requests. 
The most we use classic or LR, the most we discover missing feature.

I would like to know if it is deliberate or not. 

It make me thing we are paying a whole 24 bucks a month for a beta software. in fact we are paying the development of the software but our voice is not take in account,

Thats unfair from adobe.

Not syncing keywords is probably the most silly decision in Lightroom CC that Adobe has made. CC is perfect for taking you Classic Catalogue Pictures with you on the road on a smaller device, so that you can cull through photos (which works fine) and tag them (which is not possible at all if you want to continue in Classic later).
Please Adobe have mercy on everybody an sync keywords across these platforms! And if you decide to do so, please include the Sensei-Data as well (I recently found out that they are included in the Sync-Protocoll which can be downloaded in Lightroom Classic), so it should not be that difficult).

provided that the keywords had been written into the file's metadata (using the LR Classic command Metadata > Save Metadata To File or the option Catalog Settings > Automatically Write Changes Into XMP).

and provided that you have not generated smart previews for those photos before saving metadata to file. This is because the sync process always tries to upload any existing smart preview rather than generate a new one, so if you generate them before saving metadata to file they won't have the keywords baked in. So it's a "special case" with numerous caveats.

I think many of us feel let down by Adobe's failure to implement some kind of mobile keywording that can be used with Classic.

That makes the break even worse - keywording is one of the things I really like to be able to do in Lightroom CC as is searching for images with a certain keyword to present them or select among similar images. For serious editing Lightroom CC is all but useless on mobile devices like an iPad for me...

Karl, you might be thinking of somewhat different special case: When a photo in LR Classic is first synced with LR CC, any keywords previously assigned in LR Classic get copied into LR CC, provided that the keywords had been written into the file's metadata (using the LR Classic command Metadata > Save Metadata To File or the option Catalog Settings > Automatically Write Changes Into XMP).

But in general, once a photo has been initially synced between LR CC and LR Classic, any subsequent changes to keywords in LR CC don't get synced to LR Classic, and vice versa.

No, keywords which are added in Lightroom CC to photos imported in Lightroom CC do not sync back to Lightroom Classic either.