I love seeing how other people solve similar problems. I've seen this other project [1] that is similar in idea, but the author there has opted to go for something that looks literally like a texting app. Yours looks more Slack-like, just going by the Mac version.
Likewise, I also wanted to create an app for keeping track of short notes, but I thought it would be neat to give it the UI of something like Twitter or Tumblr, so I built Minders. [2] I have to admit that not all the design ideas in my particular app work quite well together yet (such as "hearting" and replying to your own posts), but I do end up using it regularly for journaling and keeping track of interesting links.
[1] https://zhenyi.gibber.blog/gibberish-is-now-available-on-tes... [2] https://minders.ussherpress.com/