Whilst Hamilton was indeed ahead, he was not completely ahead; they were still alongside eachother.
Its not just about how far ahead in length each driver is but also their line and who is defending and who is attacking.
A defending driver who is on the inside line (usually the superior line to determine the corner) is nearly always going to have the corner.
An attacking driver who is on the outside line needs to have significantly more speed and a line which can beat the defending driver but keeping in mind the likely trajectory of the defending driver. Hence simply being alongside is not enough to determine that the attacking driver has won the corner or has earnt the right to be given the space.
The reason Grosjean's overtake worked was because Hamilton chose not to take a wide exit as presumably he didn't expect Grosjean to have the grip and speed on that line.
Hence with Maldonaldo Lewis takes a wider exit anticipating the same move - this doesn't mean Lewis is being unfair, it simply means he has chosen a better defensive move. It doesn't give Maldonaldo a right to make the same move Grosjean did, though he can (and did) attempt it.
The whole point of a good overtake is forcing the defending driver to concede the position - to put them in a position where they can no longer dictate the attacking driver takes.
Fair defending should be predictable. And good defending is being clever with it. Its up to the attacking driver to recognise the moves and come up with the correct counter.
For example, if a driver is consistently taking a hard inside line they will generally get poor exits. So the most common and easiest counter to this kind of defensive driving is a "switchback" where the attacking driver takes the normal, outside entry but cuts deep for the apex to maximise the exit and take advantage of the poor exit of the defensive driver.
A defensive driver can then re-counter this by slowing on the apex and forcing the attacking driver to match the defensive driver's speed or run a wider or tighter exit. As long as both drivers can counter each others moves then thats what builds great racing and battles.
Its when drivers drive erratically or un-predictably that it becomes unfair. Nothing Lewis did in his moves was erratic or un-predictable.
I'll also add that this why Kobayashi-style divebomb overtakes are generally frowned upon as they are not predictable and its so easy for the driver ahead to not see it coming and take them both out. But as Kobayashi has a near-100% success rate with those moves I think he's earnt the respect to get away with it.
The difference is, the F-duct took far less downforce off the car than DRS does.
True, but the point still stands. There were some corners where the drivers didn't use the f-duct because they needed the rear-downforce. Same applies with DRS and DRS is free to use in practice and qualifying anyway and we've rarely had incidents.
And think they should keep the "no DRS until after lap 3" rule though as it does make sense considering the bunching of the pack. No one wants to see the GP2-style chaos with too many cars jostling for position in one corner.
