Why you should care

Mixing JSP standard syntax and JSP XML syntax is considered somewhat common as much of the standard JSP syntax is already XML-compliant including all the standard actions. However there are certain elements that are not compliant with an XML syntax. Such elements include Comments where Standard Syntax comments are written as <%– and XML syntax comments are written as <!–. Mixing up those elements can cause readability and agility issues which can result in software that is bug and error prone.

Business Impacts

It is recommended to take care when mixing JSP standard and XML syntax because over-mixture can cause agility issues which results in greater costs and waste of resources.

CAST Recommendations

CAST recommends establishing an internal standard for code commenting. Ensuring that each application and their corresponding development team has a unified style guide, in order to standardize the type and commonality of comments.

Developers and project leaders should think about what portions of their codebase may require effort to understand and make appropriate, meaningful additions.  Nonetheless, they should avoid superfluous additions to sections that are self-explanatory. And finally there should be an emphasis on writing comments alongside the development process, rather than after the fact.

References

https://wiki.php.net/rfc/group_use_declarations