Quote from src/core/irc/ircnetworkadapter.cpp

void IRCNetworkAdapter::setChannelMode(const QString &channel, const QString &nickname, 
const QString &flag, bool bSet)
{
        /* ... */

        QString flagPrefixed;
        if (bSet)
                flagPrefixed = "+" + flag.trimmed();
        else
                flagPrefixed = "-" + flag.trimmed();

        /* ... */
}

$ grep -r '" + "' src/ | wc -l
1
$ grep -r '" + ' src/ | wc -l
98
$ grep -r ' + "' src/ | wc -l
118

$ grep -r "\.append(" src/ | wc -l
72