I just updated the JCE extension to JCE Pro(version - 2.9.10) in Joomla 3.9.27. Now, in the article content in Joomla at the admin panel, I am adding the style tag with the comment like below
<style>
<!--
.wrapper {
display:block;
padding: 10px;
}
-->
</style>
Now when I switch the editor to the Code tab then it adds the space between < & ! like below
<style>
< !--
.wrapper {
display:block;
padding: 10px;
}
-->
</style>
before updating to the JCE pro it worked fine.
Please check the below image for more details.
Editor tab


If you want to comment code in CSS, you wrap it inside
/* */marks, egYou've unintentionally used the HTML comment marks
<!-- -->