Overwrite others sections in case there is an empty section title about tw-section

[kookma]

Yes, this is a limitation in the current implementation!
Have you tried the above example with simple change:
When enter the body of tiddler for the second heading use two spaces e.g !!<space><space>
so your body looks like this

!! Section 1

S1

!!  

Note to the two spaces in front second !!

[byzheng]

I don't think it is a big problem for me. It is very easy to avoid through writing the full section title before save it.

I just thought it will be useful to report here.

[kookma]

There was some discussions on the forum on this. The recommendation is to use distinct header.
You may note if you create two exactly similar sections they overwrite each other. This is a limitation and I hope I can address this in future revisions