We usually handle this by instructing the editors to add three dashes where there's a possible line break.

E.g.

Allokerings---strategi­---sammanslutnings---förbundet 

public static string ReplaceDashesWithShy(this string text) {
    return string.IsNullOrEmpty(text) ? text : text.Replace("---", "­");
}

Add a shared displaytemplate in ~/Views/Shared/DisplayTemplates/String.cstml

@{
    var str = Model as string;
}
@if(str != null) {
    @( WebUtility.HtmlDecode(str.ReplaceDashesWithShy()) )
} else {
    @Html.DisplayFor(model => model)
}

That will handle any strings with ---. Or are you looking for some solution for xhtmlstrings as well?

Regarding the automatic version of this you must use an external library, I've never used a c# version of this but found the Hyphenator.Net library 

E.g

using Hyphenator;

var hyphenator = new Hyphenator.Hyphenator("sv"); // "sv" for Swedish
string result = hyphenator.HyphenateText("avstavning");
Console.WriteLine(result);  // Outputs: av-stav-ning

I have used the Pyphen library in python and know that that works pretty well

import pyphen
dic = pyphen.Pyphen(lang='sv_SE')
print(dic.inserted('avstavning'))  # => av·stav·ning

If the Hyphenator.Net library doesn't work you can always wrap Pyphen in a container or so and call it during the publish event and parse your HTML that way.

Found it! The editor had made copy/paste from the browser and you the get the soft hyphen included. Then when publishing the page it goes down to the database. So it was an editor issue.