Why is this an issue?

Multiple fields should not be declared on a single line. This affects readability, is less convenient to change for version control purposes, and can be error-prone to modify.

How to fix it

Separate the grouped fields into separate lines.

type
  TMyType = class(TObject)
  private
    FId, FAge: Integer;
  end;

type
  TMyType = class(TObject)
  private
    FId: Integer;
    FAge: Integer;
  end;

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