Japanese has some sets of characters which look very similar or even identical. Obviously, context is usually more than enough to distinguish which character is intended, but I'm wondering if there are subtle differences which can be used to disambiguate. It's easy enough to compare characters in computer fonts, so my question is really more about handwriting.
ー (katakana), 一 (kanji) and — (em dash)
The first two can be distinguished from the last one in Minchō-type fonts, and usually it is possible to distinguish between all three. In vertical writing the katakana bō and the em dash are oriented vertically so is easily distinguished from the kanji ichi.
What about in handwriting or Gothic-type fonts? I suspect they are indistinguishable then, but counterexamples are welcome.
ロ (katakana) and 口 (kanji)
In print, katakana ro is usually printed a little bit smaller than kanji kuchi. In some of the fonts I have the final stroke of katakana ro protrudes to the right, while the penultimate stroke of kanji kuchi protrudes downwards.
カ (katakana) and 力 (kanji)
Like the above, katakana ka is usually printed a little bit smaller than kanji chikara; but I've also noticed that the little hook is subtly different for katakana ka, and that in some fonts katakana ka has a bit of a rightward slant or curvature.
ニ (katakana) and 二 (kanji)
- エ (katakana) and 工 (kanji)
- タ (katakana) and 夕 (kanji)
ト (katakana) and 卜 (kanji)
Other than size, it seems like the only way to distinguish these pairs in Minchō-type fonts is to rely on the tendency for katakana to have more brush-like strokes than the kanji.
ハ (katakana) and 八 (kanji)
These are usually easy to distinguish in print, even in brush-type fonts, since the last stroke of katakana ha is of a different type from the last stroke of kanji hachi. What about in handwriting?
え (hiragana) and 之 (kanji)
These are easily distinguished in print and good handwriting, but I have trouble making them distinct in my handwriting.
へ (hiragana) and ヘ (katakana)
Is there any difference between these two? They are identical in Hiragino Mincho, for instance...