Why is D written as Đ in Japanese handwriting?

Question

I've seen Japanese people write many letters/numbers "strangely". The most common one is D which is written with a stroke like this Đ

Why is that? Are there any other letters that are written differently from how it's done in Western countries?

Edit:

IIRC the number 4 is also written with a longer vertical stroke because I remember seeing Japanese people elongated foreign people's number 4 to make it clearer. I suppose because they think it's similar to Katakana ム?

Note that I do know that Japanese people don't write 7 with the horizontal stroke like the above font but with a hook above, because when I first learnt the language my teacher told me that they don't understand what that is. I did hear Japanese people asking what that 7 symbol is, or confirm if it's the number 7 when they're familiar with foreign handwriting.

And there are non-programming versions without the stroke on 0 as well:

More examples can be found on https://www.freejapanesefont.com/category/handwriting/

Answer 1

You're probably working as programmer or accountant, or you won't actually see many people in Japan write in this style, because those slashes are added to reduce misreading possibility in quick handwriting. For what it's worth, I rarely write letters like this myself.

Here is a more complete example from the font.

Who made it is clearly a programmer (see the link). It's their style to put slashes on 0, 7, D, O (top bar), and Z to make sure they wouldn't misread the source code (broadly speaking, serifs of I are the same kind).

If you ask why it's allowed to write letters like this, the reason will be that Japanese are a sort of people who only recognize the basic alphabet, i.e.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Of course, Vietnamese people wouldn't please with the use of Đ, as much as Polish people frown on Ƶ (they are different letters in their alphabets). Moreover, Turkish people wouldn't agree with i being the lower case of I in the first place. Even not as extreme as this, people write letters in more or less different ways around the world. The Latin letters' world is diverse.

Answer 2

Not sure if that's the explanation but I found this page which seems to suggest adding various strokes to letters to ensure they're not confused for other similar-looking (especially to the Japanese eyes) ones, similar to how some fonts use slashed zero to distinguish it from the letter O.

BTW, I did a similar thing while at university: in quick handwriting it may be difficult to distinguish m from w or n from u (and especially in Russian cursive, ш from т and и from п), so I often added bars above or below those letters in my notes to reduce confusion.

Answer 3

I am not sure this is concrete enough to be considered an answer, but I will post here.

I've never seen this "D" before in Japanese fonts; it definitely is not common.

I assume that it is purely a stylistic choice. Whoever wrote that probably did not know that is a different letter, but only saw it as a "cool-looking D". Kind of like how English speakers playfully use "я" in place of "R", even though they are completely different letters.