Typically, modern web browsers will automatically merge certain letter combinations, such as 'f' and 'i', into a single character known as a ligature. While this can enhance readability, it may not always align with a designer's preferences.
I personally encountered this problem in Chrome (Version 53.0.2785.101). Although I cannot guarantee, it seems likely that this issue exists in other versions of Chrome as well.
Chrome: https://i.stack.imgur.com/fmNEr.png 'f' and 'i' are combined multiple times
Edge: https://i.stack.imgur.com/rYdkH.png
IE11: https://i.stack.imgur.com/l4Yti.png
In this particular scenario, I sought a solution to disable this feature.