Given that comments use a markup, it'd help a lot to have comment preview.

I've seen this work in a few ways on the internet.

Trac shows you the preview while you're writing the comment in a different box. I like that--it's pretty helpful.

MediaWiki has a "preview" button and shows you what it'll look like when it's posted. Pyblosxom works this way, too. This works, but it's far less convenient.

I'd prefer us to implement the first. Maybe use AJAX to round-trip formatting the comment to get the preview every few seconds? Is that safe?

We're using 0.12.2. We should upgrade to 1.0 (or whatever is latest when we do this work).

1.0 release notes are here: ​http://trac.edgewall.org/wiki/TracDev/ReleaseNotes/1.0

Can be seen on my install: ​https://warpr.org/u/warp/m/dsc00427/

After clicking the openstreetmap link I get the correct coordinate when I change the mlat= argument from 2.13808555556 to -2.13808555556.