English speakers tend to write css rules like:

.icon {
  margin-right: 0.5em;
}

This makes perfect sense when the writing direction is ltr but as soon as it is flipped to rtl the margin will look completely wrong. Using a rule like:

.icon {
  margin-inline-end: 0.5em;
}

Will result in the will apply the margin to the end of the inline element (so the right or left depending on the writing direction).