This feature can be added easily using an 2nd optional argument to the \section and \subsection commands, which is used for the 'status'.
This does no harm if the argument is empty.
\documentclass{article}
\usepackage{xparse}
\makeatletter
\let\latex@@section\section
\let\latex@@subsection\subsection
\RenewDocumentCommand{\section}{somO{}}{%
\IfBooleanTF{#1}{% Is it the starred version (s)?
\latex@@section*{#3}%
}{% Nope
\IfValueTF{#2}{% Is the 2nd optional argument in action?
\latex@@section[#2]{#3\hfill\textit{#4}}
}{% No 2nd optional argument, write `#3` to the ToC instead.
\latex@@section[#3]{#3\hfill\textit{#4}}
}%
}%
}
\RenewDocumentCommand{\subsection}{somO{}}{%
\IfBooleanTF{#1}{%
\latex@@subsection*{#3}%
}{%
\IfValueTF{#2}{%
\latex@@subsection[#2]{#3\hfill\textit{#4}}
}{%
\latex@@subsection[#3]{#3\hfill\textit{#4}}
}%
}%
}
\makeatother
\begin{document}
\tableofcontents
\section{Zeroth Topic}[Not started]
Some text goes here.
\section{First topic}[Completed]
Some text goes here.
\section{Second topic}[Not started]
Some text goes here.
\section{Third topic} % no comment
Some text goes here.
\section{Fourth topic} % no comment
Some text goes here.
\subsection{First Subtopic}[Minor progress]
Some text goes here.
\subsection{Second Subtopic}
Some text goes here.
\end{document}

Update
A version which allows switching off status content:
\documentclass{article}
\usepackage{xparse}
\makeatletter
\let\latex@@section\section
\let\latex@@subsection\subsection
\newif\ifusestatus
\usestatustrue
\RenewDocumentCommand{\section}{somO{}}{%
\IfBooleanTF{#1}{%
\latex@@section*{#3}%
}{%
\ifusestatus
\edef\@@tempa@@{#4}
\else
\edef\@@tempa@@{}
\fi
\IfValueTF{#2}{%
\latex@@section[#2]{#3\hfill\textit{\@@tempa@@}}
}{%
\latex@@section[#3]{#3\hfill\textit{\@@tempa@@}}
}%
}%
}
\RenewDocumentCommand{\subsection}{somO{}}{%
\IfBooleanTF{#1}{%
\latex@@subsection*{#3}%
}{%
\ifusestatus
\edef\@@tempa@@{#4}
\else
\edef\@@tempa@@{}
\fi
\IfValueTF{#2}{%
\latex@@subsection[#2]{#3\hfill\textit{\@@tempa@@}}
}{%
\latex@@subsection[#3]{#3\hfill\textit{\@@tempa@@}}
}%
}%
}
\makeatother
\begin{document}
\tableofcontents
\section{Zeroth Topic}[Not started]
Some text goes here.
\section{First topic}[Completed]
Some text goes here.
\section{Second topic}[Not started]
Some text goes here.
\section{Third topic} % no comment
Some text goes here.
\section{Fourth topic} % no comment
Some text goes here.
\subsection{First Subtopic}[Minor progress]
Some text goes here.
\subsection{Second Subtopic}
Some text goes here.
\end{document}
\sectioncommand ;-) – Jun 01 '16 at 18:02