You only get a very partial view of the ticket's restrictions on MMB. The fare basis code (I4ABCD) is very useful to a clued up traveller to know what their options are for change or cancellation; and as Royce points out it can be quite tricky to find that out, especially in the period between booking and ticketing.

My own three annoyances
1) Only one change generally allowed online, not two. So if you have moved your inbound flight you can't upgrade your outbound without a telephone call.
2) Not getting POUG online if there are multiple classes from a connecting flight. This severely limits those of us who live in the "regions".
3) Probably for similar reasons, on travel agent bookings, if there is a connecting domestic flight you cannot upgrade using Avios, since domestics flights can't be upgraded and the screen layout falls over.