Beanman
This is a common issue raised with new users, and there are plenty of work arounds. There are good reasons for the default behaviour but it does challenge long learned habits.
There are some activities and projects occurring that will impact this and give wiki text authors a lot more possibilities so keep your eyes open.
However you may find in WYSIWYG editors such as Microsoft word etc you are often using double<enter> for paragraph breaks as well, however we do it, we do need to differentiate between lines and paragraphs.
Yet when using wiki text it is more like a simple text editor so needing to indicate the paragraph seems unusual, but given wiki text gives you a lot of formatting and presentation options its ultimate objective is similar to WYSISWYG outputs.
Having used tiddlywiki in its various versions for more than a decade now I am very familiar with it, yet every now and then it annoys me, others and new users. Hence the ongoing work
It seems Eric's great suggestion has some other effects, so I am looking at a way to make it conditional.
Tones