Incorrect syntax for ABAP Doc command '&1 &2'

What causes this issue?

A wrong syntax is used for an ABAP-Doc-command to document a parameter
or exception.
For methods, events, function modules and form routines you can also
document parameters and exceptions. The following syntax is used to
document parameters and exceptions:
Parameters
<EX>@parameter <parameter name> | <parameter documentation></>
Class-based exceptions ,,
<EX>@raising <exception name> | <exception documentation></>
Classic exceptions ,,
<EX>@exception <exception name> | <exception documentation></>
Example
<EX>"! This method compares two sources and returns whether they
"! are identical.
"!
"! @parameter source1 | First source code text
"! @parameter source2 | Second source code text
"! @parameter ignore_case | X => text will be compared case
insensitive
"! @raising cx_invalid source | Is raised if an empty source code text
is passed
methods compare
importing
source1 type text
source2 type text
ignore_case type abap_bool
returning
value(result) type abap_bool
raising
cx_invalid_source.</>

System Response

Syntax check returns a warning.

How to fix this error?

Use the correct syntax for ABAP-Doc-commands like @parameter.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.