"The national broadband network is a wonderful commitment to getting everyone connected." If you're a public servant, I dare you to post this on the internet – say, via Facebook or Twitter. I'll give you extra kudos if you use your real name.

So what's the catch? Surely, it's an inoffensive opinion that's held by many people – perhaps even a majority of Australians. How could it possibly land a public servant in trouble?

That comment was made by the "inventor of the internet", Sir Tim Berners-Lee, before last year's federal election. At the time, the NBN was among the policies that most clearly differentiated Labor from the Coalition. Berners-Lee also described the NBN as a "brilliant foundation" for Australia.

Now, I admit I'm drawing a rather long bow here, but one could mount a case that, had a public servant posted that opinion online, they would have breached the Public Service Act. How? The act requires all APS staff to be "impartial" and "apolitical". And the Public Service Commission's guidelines on online comment – which again fell under critical scrutiny this month – say public servants should refrain from expressing an opinion that is "so harsh or extreme in its criticism of the government, an MP from another political party, or their respective policies, that it raises questions about the APS employee's capacity to work professionally, efficiently or impartially".

It's easy to see how someone, for whatever purpose, could dress up apparently innocuous praise of the NBN as "extreme" commentary. In the context of an election campaign in which the NBN was a bitterly contested policy, describing it with epithets such as "wonderful" and "brilliant" could be seen to imply strong criticism of the Coalition, which campaigned against it.

And here we see one of the many problems with the bureaucracy's efforts to control how public servants express (and suppress) their political views. The guidelines do not clearly distinguish what "harsh or extreme" means, nor is there much case law to clarify that. If a politician, or even a member of the public, questions a public servant's impartiality, that may be all it takes for a disciplinary investigation to commence.

Of course, in practice, few public servants will be affected by the bureaucracy's social media policies. Like the labels that remind us not to swallow batteries, or the signs McDonald's uses to warn customers that its coffee is hot, workplace rules are often designed with the most unlikely cases in mind. Most public servants, even those with strong political views, manage to express their opinions in ways that don't undermine perceptions of their professionalism. The government's broad guidelines give agencies and managers the discretion to decide when a staff's comments go too far. Most public servants who voice a strong political opinion will not be questioned about it, let alone disciplined for doing so.

Yet wherever discretionary power exists, so too does the opportunity to abuse that power. And, in the absence of clear rules that set out public servants' rights, and which  distinguish a "harsh" political comment from an acceptable opinion, the guidelines will almost certainly be applied inconsistently.

It's a pity that one of the first attempts to test the legality of the government's social media guidelines was, in many ways, such an imperfect case. The Immigration Department began the process of sacking an employee, Michaela Banerji, in 2013, and the matter dragged through various stages, courts and tribunals until the two parties settled last month. Banerji had used a pseudonymous Twitter account to criticise refugee detention policies; that is, her tweets not only expressed her political beliefs but reflected on her employer, too. Also, while at the department, she had continued working in a second job as a psychoanalyst beyond the period for which she had formal approval. Court records show she had a "history of workers' compensation claims", had complained formally about "adverse treatment in her workplace" and had accused her boss, Sandi Logan, of bullying her. Clearly, her relationships with colleagues were less than ideal. She also described herself as a "conscientious objector" to immigration detention, suggesting it could be difficult for her to argue she was impartial in her work.

Nonetheless, in arguing against her dismissal, she said policies that prevented public servants from voicing their personal views breached their freedom of political expression, which the High Court has found is an implied right in the constitution. Unfortunately, the Federal Circuit Court did not examine this argument in detail.

At some point in future, a public servant will find themselves under investigation for expressing personal political views and, unlike Banerji, those views will not relate directly to their work. A court will then need to tackle the question that Banerji raised and make a clear ruling on public servants' constitutional rights.

The commonsense solution is, of course, to judge government employees by how they perform at work, not by what they say and do in their private lives. Public Service Commissioner Stephen Sedgwick said this week "we want public servants who will be ‘of the community' and no doubt public servants will share in the spectrum of beliefs that are found in the community". In justifying the policy encouraging staff to self-censor their views, he warned that posting opinions online "can have far-reaching consequences". Yet we are left to guess what those special consequences could be.

If Sedgwick were to apply his logic consistently, he would seek to ban public servants from joining political parties, too. After all, signing up to a party is one of the most extreme ways a citizen can express their political partiality – it's certainly a more radical step than any tweet or Facebook post. Sedgwick won't suggest it, of course, because he knows public servants have, for decades, managed to be both party members and excellent employees.

I know public servants who are  passionate (dare I say "extreme") supporters of Labor, the Liberals and the Greens. They do their jobs to the best of their ability, regardless of who is in power and what they say outside work. I dare say most Canberrans know such people. Sedgwick need not fear them. They will not destroy the integrity of the public service, because they are its integrity.

Markus Mannheim edits The Public Sector Informant.