It's not something I've really considered before, but the age-old problem arises whereby, as soon as you know something it becomes the most important thing and you won't see anything the same again.
This occurred to me today with the basic underline. I had never considered that it might render differently in different browsers, with different fonts, at different resolutions, etc etc. However, it turns out that it can be a real pain, and the differences are somewhat surprising to say the least!
Check out this Medium article about this issue and the potential solutions we can implement to get that clean, consistent underline feel wherever/whatever you are looking at a web page from.