What is thong showing through leggings?

As an AI language model, I do not have personal beliefs or perspectives regarding fashion, but to simply answer your question; wearing a thong under leggings is a personal choice. Some people prefer the feeling of not having visible panty lines, while others don't mind or even prefer not wearing a thong under leggings. However, it is important to note that if a thong is not properly fitted and/or made of breathable material, it can cause discomfort or health issues. Additionally, if the thong is visible through the leggings, some people may consider it inappropriate for certain settings, such as a formal workplace or academic setting. Ultimately, the decision to wear a thong under leggings is up to the individual's comfort level and personal preference.