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In parts of Europe, online news sites are adopting measures to discourage readers from commenting because there are just too many posts for editorial staff to monitor.

Guest blogger Tomáš Bella reports on the problem and solutions like his own start-up business, Piano, which bundles media groups together behind a single paywall, allowing users to pay and log in once for access to many sites.

Tomáš (below) is a former editor-in-chief at Sme.sk, in Slovakia, whose use of its enthusiastic readers he writes about here: 

Journalists from the most respected newspapers in Central Europe routinely have to put up with readers telling them that 'we are not coming to your site for the news, but for what other readers say about it'. There are often hundreds, or even thousands, of comments beneath the most popular articles online.

The most popular news site in Slovakia, Sme.sk, belonging to the newspaper SME, is visited by 1.5 million unique readers a month (in a country with a population of 5.5 million). Until very recently, the editors responsible for the front page also had to go through thousands of readers' comments that appeared daily and delete the inappropriate ones.

To stem the flow, media organisations have set up systems to discourage comments.

So if you want to comment on an article at the most popular Czech news site, Novinky.cz, you must fill in your real name and postal address and wait a few days before an access code arrives by post. Only then, using your code, are you allowed to comment - and your name and home town are displayed with your comments.

This radical approach has worked. Readers' comments have dropped from 50,000 to 4,000 a day. But the number of page views has risen by a third because the quality of the content has shot up. 

Other sites in Central Europe, such as Pravda.sk, one of the leading dailies in Slovakia, require readers' authentication via SMS before allowing comment.

There's a long history of user engagement in Central Europe. Local media often allowed discussion beneath their articles earlier than their Western European counterparts; usually in the mid- to late 1990s.

This was partly because they were less worried about legal issues, and partly because they did not have much choice: their editorial resources were so limited that asking readers to fill in the gaps seemed an obvious solution.

Despite the effect of existing measures, some media organisations still feel they need a radical solution. Thus the decision to ask readers to pay for being allowed to comment.

It will hopefully further raise the quality of debate and stop internet trolls from setting up accounts. So in April several of the most popular news sites in Slovakia will start charging €2.90 per month, through Piano, for the privilege of writing comments and for access to other premium features on all the sites.

While this may amount to discouraging engagement, news organisations have also learnt to value their readers' involvement.

Blog.sme.sk is Europe's oldest newspaper-owned blogging platform, established in 2004 by SME. It currently has over 18,000 registered bloggers, with 1,000 of them active in any month.

During the London bombings in 2005, there were no Slovak media correspondents in Britain. But Sme.sk had 15 bloggers in London that day; one of them on the Tube very near to one of bomb sites.

Minutes after the incidents, newspaper staff began contacting their bloggers to ask for information. Several articles from the blogs were quoted in the newspaper, including one full-page account of the day.

Blog.sme.sk has also become a major platform for political discussion in Slovakia.

One example is blogger Natália Blahová, who started writing about the problem of orphanages in Slovakia in 2006. She gained a significant number of followers and her articles were often reprinted in newspapers. Later, she turned the blog into the main platform for her campaign to speed up the process of adopting children.

In 2009, she was recruited as the expert in this area by a new political party, and she became a member of parliament in 2010. Natália Blahová is now directly involved in changing the legislation that she has been criticising on her blog.

Her party, Freedom and Solidarity, is sometimes dubbed the 'internet party', since many of its prominent members campaigned on blogs and Facebook, and its head, Richard Sulík, is well known not only for blogging but for passionately arguing with his critics on internet forums. He still blogs and discusses issues with the readers of his blog in his new job - as chairman of the Slovak parliament.

Tomáš Bella talked to Journalism.co.uk about his Piano start-up here.