Steps to reproduce:
1) Create a content page
2) Drag the Free HTML component on it from the default fragments list.
3) Edit and enter a simple HTML in it.
Example: <!-- Comments --> <h1>Comments Testing</h1>
4) Save it.
5) If you open it again the comments won't be there.
Environment: Liferay 7.2 with Fix pack DXP-7
Expected Behavior: Comment should be present along with the text.
Actual Behavior: Comment is not present, only text is present after reopening the edit option.