Players are not interacting with inventory so more hints needed. The documentation has all the key mappings and can be downloaded here:
http://xaxero.com/Documentation.pdf
The hint stays on the screen until the player starts adding inventory.
Added more prompts at start of game
Source: Steam Community (opens in a new tab)
Build and release context
Recorded Steam release date:
Within one calendar day of this post (UTC). The listed date does not establish an exact launch time.