Just tested it and it works great:
root@manager ~ # adduser acme2
Adding user `acme2' ...
Adding new group `acme2' (1006) ...
Adding new user `acme2' (1006) with group `acme2' ...
Creating home directory `/home/acme2' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
Changing the user information for acme2
Enter the new value, or press ENTER for the default
Full Name []:
Room Number []:
Work Phone []:
Home Phone []:
Other []:
Is the information correct? [Y/n] y
root@manager ~ # su acme2
bash: alias: -wSc: not found
acme2@manager:/root$ cd /home/acme2/
acme2@manager:~$ git clone https://github.com/Neilpang/acme.sh.git
Cloning into 'acme.sh'...
remote: Counting objects: 5355, done.
remote: Compressing objects: 100% (10/10), done.
remote: Total 5355 (delta 4), reused 6 (delta 2), pack-reused 5343
Receiving objects: 100% (5355/5355), 1.99 MiB | 0 bytes/s, done.
Resolving deltas: 100% (2893/2893), done.
acme2@manager:~$ cd acme.sh/
acme2@manager:~/acme.sh$ git checkout 2
Branch 2 set up to track remote branch 2 from origin.
Switched to a new branch '2'
acme2@manager:~/acme.sh$ ./acme.sh --install
[Sat Jan6 11:56:33 CET 2018] Installing to /home/acme2/.acme.sh
[Sat Jan6 11:56:33 CET 2018] Installed to /home/acme2/.acme.sh/acme.sh
[Sat Jan6 11:56:33 CET 2018] Installing alias to '/home/acme2/.bashrc'
[Sat Jan6 11:56:33 CET 2018] OK, Close and reopen your terminal to start using acme.sh
[Sat Jan6 11:56:33 CET 2018] Installing cron job
no crontab for acme2
no crontab for acme2
[Sat Jan6 11:56:33 CET 2018] Good, bash is found, so change the shebang to use bash as preferred.
[Sat Jan6 11:56:34 CET 2018] OK
acme2@manager:~/acme.sh$ exit
exit
root@manager ~ # su acme2
acme2@manager:/root$ cd /home/acme2/
acme2@manager:~$ which acme.sh
acme2@manager:~$
acme2@manager:~$ export ISPC_User="xxx"
acme2@manager:~$ export ISPC_Password="xxx"
acme2@manager:~$ export ISPC_Api="https://manager.roleplayer.org:8080/remote/json.php"
acme2@manager:~$ export ISPC_Api_Insecure="0"
acme2@manager:~$ acme.sh --test --issue -d roleplayer.org -d *.roleplayer.org --dns dns_ispconfig
[Sat Jan6 12:03:50 CET 2018] Using stage ACME_DIRECTORY: https://acme-staging-v02.api.letsencrypt.org/directory
[Sat Jan6 12:03:51 CET 2018] Registering account
[Sat Jan6 12:03:52 CET 2018] Registered
[Sat Jan6 12:03:52 CET 2018] ACCOUNT_THUMBPRINT='xxx'
[Sat Jan6 12:03:52 CET 2018] Creating domain key
[Sat Jan6 12:03:52 CET 2018] The domain key is here: /home/acme2/.acme.sh/roleplayer.org/roleplayer.org.key
[Sat Jan6 12:03:52 CET 2018] Multi domain='DNS:roleplayer.org,DNS:*.roleplayer.org'
[Sat Jan6 12:03:52 CET 2018] Getting domain auth token for each domain
[Sat Jan6 12:03:53 CET 2018] Getting webroot for domain='roleplayer.org'
[Sat Jan6 12:03:53 CET 2018] Getting webroot for domain='*.roleplayer.org'
[Sat Jan6 12:03:53 CET 2018] Found domain api file: /home/acme2/.acme.sh/dnsapi/dns_ispconfig.sh
[Sat Jan6 12:03:53 CET 2018] Getting Session ID
[Sat Jan6 12:03:53 CET 2018] Retrieved Session ID.
[Sat Jan6 12:03:53 CET 2018] Getting Zoneinfo
[Sat Jan6 12:03:53 CET 2018] Retrieved zone data.
[Sat Jan6 12:03:54 CET 2018] Retrieved Server ID
[Sat Jan6 12:03:54 CET 2018] Retrieved Zone ID
[Sat Jan6 12:03:54 CET 2018] Retrieved Client ID.
[Sat Jan6 12:03:54 CET 2018] Added ACME Challenge TXT record to zone.
[Sat Jan6 12:03:54 CET 2018] Found domain api file: /home/acme2/.acme.sh/dnsapi/dns_ispconfig.sh
[Sat Jan6 12:03:54 CET 2018] Getting Session ID
[Sat Jan6 12:03:54 CET 2018] Retrieved Session ID.
[Sat Jan6 12:03:54 CET 2018] Getting Zoneinfo
[Sat Jan6 12:03:54 CET 2018] Retrieved zone data.
[Sat Jan6 12:03:54 CET 2018] Retrieved Server ID
[Sat Jan6 12:03:54 CET 2018] Retrieved Zone ID
[Sat Jan6 12:03:54 CET 2018] Retrieved Client ID.
[Sat Jan6 12:03:54 CET 2018] Added ACME Challenge TXT record to zone.
[Sat Jan6 12:03:54 CET 2018] Sleep 120 seconds for the txt records to take effect
[Sat Jan6 12:05:55 CET 2018] Verifying:roleplayer.org
[Sat Jan6 12:05:58 CET 2018] Success
[Sat Jan6 12:05:58 CET 2018] Verifying:*.roleplayer.org
[Sat Jan6 12:06:01 CET 2018] Success
[Sat Jan6 12:06:01 CET 2018] Getting Session ID
[Sat Jan6 12:06:01 CET 2018] Retrieved Session ID.
[Sat Jan6 12:06:01 CET 2018] Retrieved Record ID.
[Sat Jan6 12:06:01 CET 2018] Removed ACME Challenge TXT record from zone.
[Sat Jan6 12:06:01 CET 2018] Getting Session ID
[Sat Jan6 12:06:01 CET 2018] Retrieved Session ID.
[Sat Jan6 12:06:01 CET 2018] Retrieved Record ID.
[Sat Jan6 12:06:01 CET 2018] Removed ACME Challenge TXT record from zone.
[Sat Jan6 12:06:01 CET 2018] Verify finished, start to sign.
[Sat Jan6 12:06:02 CET 2018] Cert success.
-----BEGIN CERTIFICATE-----
[...]
-----END CERTIFICATE-----
[Sat Jan6 12:06:02 CET 2018] Your cert is in/home/acme2/.acme.sh/roleplayer.org/roleplayer.org.cer
[Sat Jan6 12:06:02 CET 2018] Your cert key is in/home/acme2/.acme.sh/roleplayer.org/roleplayer.org.key
acme2@manager:~$ openssl x509 -text -noout -in .acme.sh/roleplayer.org/roleplayer.org.cer | grep DNS
DNS:*.roleplayer.org, DNS:roleplayer.org
acme2@manager:~$