I've checked, it's definitely signed:

  ; <<>> DiG 9.11.0-P1 <<>> ed25519.nl +dnssec
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 594
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
  
  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags: do; udp: 512
  ;; QUESTION SECTION:
  ;ed25519.nl.			IN	A
  
  ;; ANSWER SECTION:
  ed25519.nl.		1341	IN	RRSIG	A 15 2 3600 20171012000000 20170921000000 27662 ed25519.nl. Z62ywpWQ4ahOs0DZxIs3OAY67qc226z6rs8k8q2i/hdwQAjz5EL5ZJke t25LD88wx5kGY5ru6Dvfrd7KvODCAg==
  ed25519.nl.		1341	IN	A	77.72.150.82

  ;; Query time: 55 msec
  ;; SERVER: 8.8.8.8#53(8.8.8.8)
  ;; WHEN: Wed Sep 27 20:44:46 EDT 2017