Below is an image showing that the button is not properly aligned next to the textarea:
https://i.sstatic.net/2LeXv.png
Here is the HTML code snippet:
<div>
<form>
<textarea name="comment" id="new-post" rows="2" cols="45" placeholder="Add a comment">
</textarea>
<button type="submit" class="btn btn-primary float-right" style="display: inline-block;"
align="right">Add comment</button>
</form>
</div>