Can a compass have its polarity reversed so that the end marked "north" points south and vice versa?
If so, what could one do to prevent and fix this problem?
They certainly can and it is caused by,
Please be aware that a reverse polarity is caused by exposing your compass to articles with iron content (something as simple as being placed next to a pair of scissors or a knife for a length of time, microwaves, high tension wires, etc.).
Magnetic fields exist around many items we commonly carry with us on the hill; mobiles & smart phones, magnets hidden inside mobile phone cases, avalanche transceivers, radios, personal locator beacons, GPS, cameras, car keys, small magnets on belt fastenings
The way to prevent this is to keep it away from iron objects and ones with strong magnets.
A conscious effort is required to keep the compass isolated from other gadgets, from phones and radios, to digital cameras, GPS, avalanche transceivers and SPOT devices. Try experimenting with all your devices near your compass so that you are aware of the ones that have a significant affect and keep them apart whether using them or storing them.
The way to fix this is,
It is possible to 'reverse' the reversed polarity using a strong magnet. This can be achieved by quickly flicking the magnet outwards along the 'north' end of the needle. Repeat vice-versa. Always ensure you compare with a compass that is known to be correct.
Some manufactures will also fix it for you.