When it comes to, say, manifesto promises, if you have a small left-wing party that people expect to get about 10% of the votes, their manifesto might say that if they form the government, they'll do all these things, but the voters know they're not going to form a government on their own. What it means to vote for them is that you want their influence on government. They won't be able to achieve everything they promised, but they will have some input into government. Voters understand the rules of coalition governments. Voters understand that voting for someone means to strengthen their voice, hopefully to strengthen their voice in government, not that they're going to do everything that's in their manifesto.
When it comes to ministerial accountability, the practice in this country is that a lot was inherited from the British practice, perhaps as in Canada. We're not experts on Canadian politics, but it means that government's collective responsibility is very strong. All ministers go out and defend the governmental line. You don't get ministers arguing with each other in public. They have their arguments in private, behind closed doors, but they all defend the government line.
Coalition governments in this country have been just as united as single-party governments; in fact, the most divided governments we've had in the past have been single-party governments, but that's not a problem anyway. There might be other problems, but government unity really isn't a problem.