Installing / setting a different system font than Roboto. Especially when it is handwritten. To my eyes, they always look horrendous.
However, a colleague recently pointed out this brilliant example of what it is like to chat with a 'handwritten' typeface. I can see how it might be 'nicer' to read messages from a friend.
It made me appreciate how easy it is to see things from only one perspective. More importantly, it makes me realize that Samsung 'rightly' has font installation as a feature.
Shows I need to embrace one of Android's core tenets - be together, not the same.