Is it okay to flap "didn't" (and "wouldn't", "couldn't", "ridden")

Question

I've tried to research this topic a lot and since I'm not a native English speaker, I can't tell whether it sounds "right" or not when you flap these words. I've found some examples on youtube of seemingly native people who flap it. Correct me if I'm wrong but I think Avril Lavigne flaps "didn't" in her song "Tomorrow You Didn't".

Somebody singing it in a song though, may not mean it is "okay" to flap didn't (or wouldn't, couldn't, etc). Is it common?

Also, I think some people differentiate "written" and "ridden" by flapping the latter. On the other hand, some people don't. Which is more common?

Thinking about this has given me multiple headaches over the last few days so if you have any input I'd be very thankful. To a native speaker, does flapping these words make them sound strange or not?

For reference: Wikipedia - Flapping

Answer 1

It depends on the social context, and most of all whether your meaning is clear. Received pronunciation might sound odd in some situations, but the most important thing is to get one's meaning across.

Answer 2

This Quora answer describes the /t/ sound:

[t] is defined as a voiceless alveolar stop in linguistics. This means your larynx or voicebox doesn’t vibrate (voiceless), and you make the sound by stopping all the air from flowing through your mouth for an instant. Alveolar means your tongue tip is just behind your teeth.

Then it gives a number of examples; this one has information needed to understand the others:

1. turret: In this word, there are two t’s. The first one, in every dialect of English that I’ve heard, is pronounced as tʰ, which is called an aspirated t. This just means that a little puff of air comes out after the t. The second t can be pronounced in the same way, and often is by Brits. It is sometimes pronounced that way by Americans, but only when we’re being very careful. Usually, Americans don’t even say a t. We use a sound called a glottal stop, written in IPA as ʔ (not a question mark, but similar). A glottal stop means cutting off the air at the glottis (in your throat) rather than with your tongue tip. MANY languages do this, but far from all. I’ve been scolded for mispronouncing other languages in this way because my native speech is like that. Possible pronunciations for turret include [tʰurɪt̚ ] (t̚ means that the speaker keeps the tongue behind the teeth and doesn’t “release” it) or [tʰurɪtʰ] or [tʰurɪʔ]. Notice that all versions have tʰ at the beginning of the word, even though the phoneme is simply t. ...

This example may be the closest to what you're asking, I think:

4. matter: British people often pronounce the /tt/ as a single tʰ. Americans usually pronounce it as [ɾ], which is an r-like flap or tap of the tongue instead of a real stop consonant. This can be explained by something called lenition. Lenition means weakening of a sound, and it commonly happens between two vowels.