> official institutions were using Twitter as a communication platform before it belonged to Musk and started to restrict visibility to non-logged in users

... thereby driving up adoption far better than Twitter itself could. Ironic or what.

I support the EU harvesting money from evil companies

Or the companies could obey the law

You appear to have posted a bit of a loaded question here, apologies if I'm misinterpreting your comment. It is, of course, the public that should decide what communication is of public interest, at least in a democracy operating optimally.

I suppose the answer, if we're serious about it, is somewhat more nuanced.

To begin, public administrations should not get to unilaterally define "the public interest" in their communication, nor should private platforms for that matter. Assuming we're still talking about a democracy, the decision-making should be democratically via a combination of law + rights + accountable institutions + public scrutiny, with implementation constraints that maximise reach, accessibility, auditability, and independence from private gatekeepers. The last bit is rather relevant, because the private sector's interests and the citizen's interests are nearly always at odds in any modern society, hence the state's roles as rule-setter (via democratic processes) and arbiter. Happy to get into further detail regarding the actual processes involved, if you're genuinely interested.

That aside - there are two separate problems that often get conflated when we talk about these platforms:

- one is reach: people are on Twitter, LinkedIn, Instagram, so publishing there increases distribution; public institutions should be interested in reaching as many citizens as possible with their comms;

- the other one is dependency: if those become the primary or exclusive channels, the state's relationship with citizens becomes contingent on private moderation, ranking algorithms, account lockouts, paywalls, data extraction, and opaque rule changes. That is entirely and dangerously misaligned with democratic accountability.

A potential middle position could be ti use commercial social platforms as secondary distribution instead of the authoritative channel, which in reality is often the case. However, due to the way societies work and how individuals operate within them, the public won't actually come across the information until it's distributed on the most popular platforms. Which is why some argue that they should be treated as public utilities since dominant communications infrastructure has quasi-public function (rest assured, I won't open that can of worms right now).

Politics is messy in practice, as all balancing acts are - a normal price to pay for any democratic society, I'd say. Mix that with technology, social psychology and philosophies of liberty, rights, and wellbeing, and you have a proper head-scratcher on your hands. We've already done a lot to balance these, for sure, but we're not there yet and it's a dynamic, developing field that presents new challenges.