I'm a big fan of the Magic Links in comments. Heck, I'm going to wear out my f, a, and q keys shortly after I wear out [ and ].
I very often find myself putting links to other questions (and answers) in comments to draw people's attention to similar and related posts but which aren't duplicates. Yes, I can just paste a raw link and that will work fine. It's not very readable, though.
In Questions and Answers, posting a raw link to a Stack Exchange post anywhere in the network will replace the raw link to a linkified title. There was a feature request to have the same sort of functionality in comments, but it was more-or-less quashed as a duplicate of the request for this feature in posts, even though it's for comments.
Lacking that functionality, I wonder if it would be possible to expand on the Magic Links for comments to include Post IDs.
In other words, a comment like:
See also: 
would automagically expand to
See also: [Why is processing a sorted array faster than an unsorted array?](http://stackoverflow.com/q/11227809)
I suppose some extra magic would have to be done to get a meta question linked just so.
Note that I'm only proposing that this Magic work on the current site, not that it should attempt to do anything across the network. Posting links to questions on other sites is rare enough that doing it the old-fashioned way is no big deal.
(This was asked about in the past, but it was just a question if it could be done. This is an actual feature request.)