I will release very soon a new version, where the tips list for an article will be displayed whether the user is logged in or not. There will be an option on how to sort tips.
In general this extension needs to be reworked. I am currently busy with the upcoming major version 5.0.0 of wallets. The most important change in 5.0.0 is that the output of all shortcodes will be theme-able. This will gradually affect all the extensions as well, including Tip the Author. One of the things I want to do after 5.0.0, is to revisit this extension and improve on the way tips are displayed, especially when there are many tips.
Since the markup will be theme-able, it will be easier to modify what is displayed and what not, either at the theme or child-theme level. There will be blog posts about these changes.
I have now pushed version 1.3.0 of the Tip the Author extension, where it is now possible for guests to see the tip list. Additionally, the admin can choose how the past tips are sorted before display.