Why “dame” is written as katakana (ダメ) in manga?

Question

"Dame" which means "not good" or "don't do that" is sometimes written in manga as katakana. Is it because katakana is used to express a strong feeling ?

Answer 1

Continuing from @sawa's list:

4. To give visual and/or very slight semantic emphasis. Almost like using bold or italics in English.

それがだめだよ！
それがダメだよ！

You can see that the latter stands out more. As for the onomatopoeia, those are often a little emphasized too, so it probably overlaps with reason 2 a good amount.

5. Plant, animal, and mineral names are often written in katakana.

Answer 2

There are several usages for katakana.

1. To describe (what feels like) Western origin words
2. To describe onomatopoeia
3. To describe the fact that it is normally written in kanji, but that it is written without it because either the writer wants to write faster, has no access to the kanji form (as in the case where the writer is given the name in a romanized transcription or the writer just heard the name), forgot the kanji form, or does not want to bother to write in kanji for any other reason.

だめ has the kanji form 駄目, and in this case, the reason is likely 3.

Answer 3

6. Style

Answer 4

7. I think it's sometimes used when it's more like a series of syllables being pronunced, rather than real Japanese. An equivalent in English would be Ginger Megg's mother saying something like "Giiingerrr!" when he's in big trouble. The English language Wikipedia says

Katakana are also sometimes used to indicate words being spoken in a foreign or otherwise unusual accent, by foreign characters, robots, etc. For example, in a manga, the speech of a foreign character or a robot may be represented by コンニチワ konnichiwa ("hello") instead of the more typical hiragana こんにちは

I haven't heard of any examples, apart from reading that McDonald's "Mr James" originally spoke only in katakana.