Okay, we’re fighting over definitions here. There is no “si” in Hepburn romanization. I am intentionally using Hepburn romanization in the article. Therefore, in my article “si” is a compile error.
You may argue with my choice, or maybe you can argue that referring to cells in Hiragana table solely by my chosen romanization is somehow bad, and I should instead be inconsistent and give the same mora two different romanizations within a single article. Is that what you’re suggesting?
First, As a basic part of Japanese language education, students are expected to be familiar with different romanization systems. If you ask a student where “si” is in the table, they should be able to find it. If a student says “it’s not in the table” then they’ve failed the lesson or there is something wrong with the teaching material.
Second: am I arguing that the choice of using Hepburn here is somehow bad? Yes, that’s correct. I think Hepburn is a bad choice here. A good choice is Nihon-shiki. JSL romanization is also fine.