Think about what happens when you send work for review. You email a link, and your client opens it. The next screen should help them look at the work and respond.
Some of them make the account. Some reply to the email with their notes instead, and now the feedback lives in your inbox rather than on the frame. Some forward it to the person who actually has opinions, who now needs their own account. Some do nothing for four days.
Keeping that first step simple helps the feedback stay with the work. The reviewer should be able to understand where to leave a note and which version they are looking at.
In Oketto, a share link opens the review without an account. Owners can optionally protect the link with a password. Enter a name so your comments have an author.
Treat a review link as access to that review and share it with the people you choose. The owner can revoke the link when access is no longer needed.