handwriting - On 原稿用紙, when are ゛ and ゜ (ten-ten and maru) supposed to occupy a square of their own?

I was intrigued by this question: What do you do if a genkoyoshi line ends with e.g. す。」? and its answer.

I'm not any good at this 原稿用紙 but I remember being told for some types of forms (which I thought followed the same rules) that you need to put the [濁点]{だくてん} (for some reason always called ten-ten and maru in the classes and contexts I heard them) into separate boxes. Was I being misled / is this still current practice for some sort of form?

Answer

The rule you mentioned does not apply to 原稿用紙 for novels and articles. Never.

However, you may be instructed to place 濁点（゛） and 半濁点（゜）into a separate box, when you have to fill some legacy paper forms at banks or government offices.

This is because 濁点 and 半濁点 consume an extra byte if you encode hankaku katakana strings into old encodings such as JIS, Shift-JIS, EUC-JP, and they have to count the number of bytes.

In my opinion, this is a very bad tradition of the fixed-length-string era, and should disappear at once.