Steps to reproduce
1. create an IMAP account with name X
2. exit claws mail
3. run claws mail
4. go to account preferences for the X account
5. change the name into the account/basic/name of account to Y
6. click ok
7. observe the folder view. The account is still named X
Just for the record, it is not reproducible here with Claws Mail 3.9.3 running on Fedora 20 (x86_64), so that raises the chance that it has been fixed in either 3.9.2 or 3.9.3. The name displayed in the folder view updates automatically.
I tried it again after manually renaming it in config files and now it changes.
What still doesn't changes are the imap paths in the advanced tab for current account.
Initially I had the account named Account2 then changed it to Gmail, the same as the IMAP folder.
Changing account name several times left folder trees in the tagsdb/#imap folder for the old names.
The renamed folder names are also left in the folderitemrc file
This has indeed been fixed, and with upcoming new release, the fix will be available also for Windows.