Definitely, heart icon means that I love this article, and that's positive response.

I don't know, however, meaning of other three icons, thinking face, raised hand and unicorn.

Thinking face is positive or negative?
Raised hand means that I have a question? (If so, you should write a comment.)

What does a Unicorn mean ?????????????

Help me, please.

postscript

Sorry, I found similar articles...

• https://dev.to/_bigblind/how-do-you-use-each-of-the-emoji-reactions-on-devto

• https://dev.to/val_baca/what-do-the-heartthinkingpraiseunicorn-buttons-mean-to-you

But why unicorn???