Is the topic particle は sometimes interchangable with けど?


By the end of the article [here](http://maggiesensei.com/2016/05/07/how-to-
use-%E3%81%91%E3%81%A9-kedo-%E3%81%A0%E3%81%91%E3%81%A9-dakedo/), the author
means that けど is used for "Introductory remarks: to bring up some topics",
such as,

> 明日｛あした｝だけど、待｛ま｝ち合{あ}わせ時間｛じかん｝どうする？
>
> 麻理｛まり｝の誕生日｛たんじょうび｝のことなんだけど、どうする？
>
> 彼｛かれ｝のことだけど、聞｛き｝いた？

Wouldn't the sentences have the same meaning as say,

> 明日｛あした｝は、待｛ま｝ち合{あ}わせ時間｛じかん｝どうする？
>
> 麻理｛まり｝の誕生日｛たんじょうび｝のことは、どうする？
>
> 彼｛かれ｝のことは、聞｛き｝いた？

I've noticed if I were to substitute は, then I would remove だ and なんだ. Does
this mean that by using は, there's less "emotion" and makes the sentence more
neutral-sounding?

On the contrary, say that I have some sentences such as,

> 私はトムです。
>
> これはペンです。

then would it be appropriate to say the following?

> 私だけど、トムです。
>
> これだけど、ペンです。




は is used to specify the topic that has been **already** brought up in the
discourse, whereas けど is used to give an introductory remark before diving
into the main theme. If you said "麻理の誕生日のことはどうする?" at the very beginning of a
conversation, it can sound unnatural and sudden. It can sound as if you were
assuming the listener had been thinking about Mari. Using けど is more natural
as the starter of a conversation.

> これだけど、ペンです。  
>  Interested in this thing? It's a pen!  
>  Look at this thing, it's a pen!

These are obviously free translation, but I hope you can catch the nuance. A
sentence like this is not impossible, but it sounds like you are explicitly
drawing attention to "this object" before disclosing it's actually a pen. You
may occasionally want a sentence like this, but you should not think it's
interchangeable with は.

Also note that が/けど/けれど are more commonly used with a longer clause rather
than a simple noun. In such cases けど is obviously not interchangeable with は.
See [this question](https://japanese.stackexchange.com/q/32824/5010) for
example.




は is used to specify the topic that has been **already** brought up in the
discourse, whereas けど is used to give an introductory remark before diving
into the main theme. If you said "麻理の誕生日のことはどうする?" at the very beginning of a
conversation, it can sound unnatural and sudden. It can sound as if you were
assuming the listener had been thinking about Mari. Using けど is more natural
as the starter of a conversation.

> これだけど、ペンです。  
>  Interested in this thing? It's a pen!  
>  Look at this thing, it's a pen!

These are obviously free translation, but I hope you can catch the nuance. A
sentence like this is not impossible, but it sounds like you are explicitly
drawing attention to "this object" before disclosing it's actually a pen. You
may occasionally want a sentence like this, but you should not think it's
interchangeable with は.

Also note that が/けど/けれど are more commonly used with a longer clause rather
than a simple noun. In such cases けど is obviously not interchangeable with は.
See [this question](https://japanese.stackexchange.com/q/32824/5010) for
example.

