It seems that your version of Azure Data Studio does not colorise the nested comments correctly. Such comments are valid in SQL. No errors will be reported for your commented query in both of Management Studio and Azure Data Studio:
/*
SELECT t.ID, t.Name, p.Prop
FROM TableName t
/*INNER JOIN SomeTable p ON t.Name = p.Name*/
GROUP BY t.Name -- All this will not be in commented text visualy
*/
(This forum seems to have a similar problem).
See the reported issue: https://github.com/microsoft/azuredatastudio/issues/19205. It seems to be fixed, but not distributed yet.
If you observe other issues, you can use the "Report Issue" command from Help menu, or the GitHub pages.