The circumstances of Ms Banerji's dismissal are well known. She used her anonymous Twitter account to publish many criticisms of her employer, the federal government. She specifically criticised asylum-seeker policy and her own department's treatment of refugees. When her manager eventually linked her to the account, the department proceeded to terminate her employment, saying her commentary had undermined her ability to be seen as impartial in her work, a legal obligation imposed on all public servants.

Over the past decade, other government employees have also hit trouble as a result of their online commentary; for voicing personal opinions they had presumed they were entitled to make.

The army dismissed one of its officers, reservist Bernard Gaynor, who had campaigned repeatedly against homosexuals in the military. SBS sacked football journalist Scott McIntyre, who had criticised the Australian military's past war crimes, after then prime minister Malcolm Turnbull raised concerns about his tweets.

There were milder cases, too - many of them. For example, Centrelink worker Daniel Starr was sacked, but then reinstated, after he used an online alter ego to criticise (and correct) the incorrect advice his agency was giving the public.

But the vast majority of cases never reach a court or tribunal; they simply result in public servants being warned or disciplined for speaking their minds. They quickly learn to shut up.

Only Comcare v Banerji went to the High Court, and this is a great shame. The entire case was a lost opportunity to clarify a murky, contested area of law. Public servants didn't need to be told not to behave like Ms Banerji - they knew that already.

Indeed, it's important to acknowledge that most public servants pride themselves on their ability to be professionally impartial in the workplace. They generally don't have great desires to be outspoken political advocates. But some, if not most, at least want a better understanding of where the boundaries lie. They want an answer to the question: "When is my view too political to be expressed publicly?"

We still don't know. One of the High Court justices, James Edelman, explained that that is deliberate. The laws that govern public servants' employment create "a boundary, albeit ill-defined, between acceptable expression of political opinions and unacceptable expression of political opinions", he wrote. In other words, this grey area of law will remain just that: a realm to be contested. It will, Justice Edelman wrote, "depend upon all the circumstances".

Justice Edelman did articulate some factors that agency heads should consider when determining whether a public servant had breached the code of conduct, such as: the public servant's seniority; whether their comments related to their duties; the tone of the comments; their audience; and what a reasonable observer might conclude about the public servant's impartiality.

But, in effect, the lack of clarity means that senior public servants will continue to overpolice the code so as to avoid causing political offence. They will overestimate their staff's capacity to undermine confidence in the public service. Many relatively harmless opinions will go unvoiced; not because they are extreme or damaging but because those who hold those views will feel cowed.

Our democracy shrank on Wednesday - just a little, but a little too much.