<svelte:component> adds unnecessary empty text nodes

[shirotech]

Describe the bug
When we use a dynamic component with a wrapped if block in an each loop, it generates multiple empty text nodes for some reason.

Logs

running Svelte compiler version 3.18.2
about:srcdoc:160 Found Text Nodes <ul>​…​</ul>​ #text #text
about:srcdoc:160 Found Text Nodes <ul>​…​</ul>​ #text #text
about:srcdoc:160 Found Text Nodes <ul>​…​</ul>​ #text #text
about:srcdoc:160 Found Text Nodes <ul>​…​</ul>​ #text #text

To Reproduce
https://svelte.dev/repl/bf64c8c4fa0b4cde9b9f93cb20168354?version=3.18.2

• Open console
• Click Add button and observe

Expected behavior
It should not generate the extraneous empty text nodes

Information about your Svelte project:

• Your browser and the version: (e.x. Chrome 52.1, Firefox 48.0, IE 10)
  It affects all browsers

• Your operating system: (e.x. OS X 10, Ubuntu Linux 19.10, Windows XP, etc)
  OSX

• Svelte version (Please check you can reproduce the issue with the latest release!)
  3.18.2

• Whether your project uses Webpack or Rollup
  Rollup

Severity
Causes layout issues on production, very severe.

Additional context
Note that using the component directly doesn't have this issue, so I assume this behaviour is not intended and most likely a bug. https://svelte.dev/repl/4fcd86502bdc4dc68511e6856adc4646?version=3.18.2

[shirotech]

I found that sometimes a node needs a dummy reference:

svelte/src/runtime/internal/dom.ts

Line 57 in 2b3c2da

return text('');

However, I've done a few tests and tried to use an empty comment instead.

export function empty() {
	return document.createComment('');
}

An empty text node actually impacts the dom structure, whereas an empty comment does not. What are your thoughts on this?

[fips0]

See also #3586

[Conduitry]

These empty text nodes are referred to internally as 'anchors' and they are needed in certain situations. #3 / #512 was about removing them where possible. I'm not sure in what issue or PR they were switched from comments to empty text nodes. We already have #3586 for discussing switching back to comments, so closing this issue.