One site I link to (Google) uses URLs with unencoded double quotes (
") in them; I usually truncate the URL until it ends in a double quote so it's not as long. This creates problems either way in the preview. I realize that quotes in URLs are unsafe, but this behavior is just confusing. It should just work the same correct way in both the preview and the rendered post.
(Let's not debate the perils of linking to Google since this happens on multiple parts of their site, whenever you search for something with double quotes. I encounter this problem because I link to Google Books.)
There was a point in time where it did work I think. But I don't remember the timeframe nor what changed.
The first problem I noticed is that the URL cannot end in a double quote, otherwise it is interpreted as the title in the preview (i.e. anything in quotes becomes the hover text). For example,
[link1](https://example.com/q="one") becomes link1, which points to the URL
If the title has spaces (which it might if you were intending to create a title), you need that space between the URL and title in order for the post to be rendered properly when you save your edit (but the preview works; see my bug report here).
The second problem, possibly a more specific version of the first problem, is that the title is interpreted as everything from the very first double quote to the last, instead of the penultimate double quote to the last double quote. So
[link_uno](https://example.com/q="uno"&true=true "Link numero uno") becomes link_uno with a title of
uno"&true=true "Link numero uno. This also only happens in the preview.
The last problem I noticed is that it's possible to break the formatting entirely, creating what looks like the end of an HTML tag and an inexplicable mix of things:
[link1st](https://example.com/q="first"&true=true) and [link2nd](https://example.com "two").
The exact conditions seem to be that there are embedded quotes in the first URL (but it can't end in a double quote) and a
title attribute for the second link. Putting a newline between the two links, even if that line isn't rendered, prevents this from happening. This, once again, all only happens in the preview.
And here's a similar problem that affects both the preview and the rendered post (much to my surprise considering the rest of this post). You can't include a title that has
https?:// (which is something I try to do when I link to Archive.is for some transparency):
[Link with hint](https://example.com/page "URL: https://example.com/")
<a href="https://example.com/page" title="URL: https://example.com/">Link with hint 2</a>
- https://example.com/">Link with hint
- https://example.com/">Link with hint 2
Yet another problem. Having quotes in the URL, followed by quotes on the inside of parens in regular text following that URL prevents the URL from ending in the right spot (this only affects the preview):
[My search](https://example.com&q="???"+WTF) start ("quote") end
- My search start ("quote") end