Muzimak, think of it as showing your appreciation to the developer for their hard work. There's a lot time and effort that they put in that you may not have realised. The devs here are mostly working alone, there's no "company" behind them. Think about it.

Even though Wazapp is free doesn't mean you should not show the dev you appreciate his work via a donation if you are in a position to do so.

You are not obligated to ofcourse, a kind word goes a long way and comments like that aren't helpful. It all helps in keeping the community alive and you should know we need that now more than ever.