Can iCal and vCard folder resources be used for syncing?

Dear List,


I have calendars and contacts on a CalDav/CardDav server. Multiple 
applications (web/android/…) access and modify entries. KDE integration is 
problematic because the *Dav resource is not able to reliably sync to the 
server. Namely, syncing from the server works and event creation also, but 
syncing any change to the server causes the resource to block badly, 
creating dirty entries that need to be manually cleaned. (This used to work 
better in the past…)

However, some KDEPIM tools (todo/Zanshin/contacts) are actually quite nice 
and I'd like to use them.

I looked at the bug reports to see if I could provide information to help 
fix the issues. There are many detailed and useful reports. There were even 
patches submitted that fixed an issue facing many users, but because that 
patch broke sync for some developers, it got reverted and never really 
looked at again to get it improved 
<https://bugs.kde.org/show_bug.cgi?id=386985>. (Not really nice that 
developers snub a large group of users like that, but I guess the excuse is 
lack of time.)

So I was looking at alternative ways to sync things. I saw after a recent 
update that iCal and vCard folder resources were added. I used vdirsyncer 
<https://github.com/pimutils/vdirsyncer> already, so I had such folders 
present on my system ready to be used. However, after creating the 
resources and pointing them at those folders, I noticed a file called 
'WARNING_README.txt' with contents

---
Important Warning!!!

Don't create or copy vCards inside this folder manually, they are managed 
by the Akonadi framework!
---

I'm wondering what exactly this means in practice, because I may have a use 
case or adapt my usage to make sure I do not get into problems.


Best,

Erik

P.S.: There are still some issues, such as the vCard folder resource not 
adding '.vcf' at the end of files and the iCal resource not actually 
detecting any entries, but those only become relevant after I know I can 
use the folder resources for syncing.