Out of curiosity, what were those features?
Fonts
I used to use Courier New and FixedSys in a manner now somewhat handled by inlinecode. I used these to indicate macros or functions from the standard library, or perhaps a variable name (outside of code in the discussion text) to help it stand out from "regular" text.
As an aside, if I had known that fonts would be removed entirely, I would have more loudly tried to get inlinecode to be [tt] for "teletype" or fixed-font.
Font Sizes
Font sizes are tremendously useful for illustrating that missed semicolon: made red and size 7 you could really see the missing punctuation. Now, notsomuch.
Sizes were also good for little "asides". Side comments or not-so-important things that could be made smaller.
Color
I used to use more and different colors to highlight items. I can barely tell the difference between the current green and the default black -- it doesn't stand out well. So essentially there is one color available.
Previously I would use multiple colors to highlight and explain more than one thing at a time. For example, a complicated sscanf statement I would use 4 or 5 colors to associate the formatting directive with its variable.
Or to point out 2 or 3 different issues in the same line of code. Or I would use it to show "error", "warning", "info" type of messages grouped by the different colors.
I also used the colors along with bold to start a "section". Similar to the bold/underline used in this post, but I found the colored titles more eye-appealing.
Text in General
Fonts and colors and sized also made for some possible amusement: "hidden" text" using colors, an interesting font it you choose to be "fancy". Some "spice" to add to the occasional bit of text.
Now it's so sterile here as to be uninteresting as a text medium. I also think of the editor as being crippled. I visit other vB and PHP forums, and I hate the "step down" from the more fully-featured sites.
Unlimited Editing Time
With snippets or the tutorial, there was once unlimited editing time. This allowed me to have several snippets refer to others. This can no longer be done without a great degree of difficulty.
It was also nice to incorporate changes mentioned in the comments back into the snippet. On a snippet or tutorial it is more important to have a fixed snippet in the first post rather than having to read 10 replies to find out the "final" version.
But you can't do this anymore. It used to be very nice to have a collection of code snippets that you could continue to keep up to date or continually improve the code.
Snippets
Snippets themselves changed from same-as-forum-post format to require a snippet and description area. It was nice to intersperse bits of code with explanations. Now, you are more able to do this in "regular"; the snippets version is a "crippled" editor.
Multi-Quoting
Previously if you quoted someone who was quoting someone, it would nest. Now if you want to do this, you have to do it manually. Yet another PITA that is default behavior elseweb.
Indenting
You can do the bullets and numbered lists, but at a time that preceded code tags, indents were used (in conjunction with fixed fonts) to display code. Some of these were done "FAQ" fashion -- intended to use the functionality at the time to display code nicely.
After a sweeping retroactive change, these were lost down the bit bucket. But a number of old posts (because of course nothing is ever deleted) still exist and now look horrible. In fact, someone posting highest-quality nicely formatted code could probably be banned after the retroactive changes.
Summary
Most of these "upgrades" were to enforce a uniformity, I guess. To avoid abuse. But currently people can abuse the formatting that is available in much the same way: all bold, all red, no code tags, using TeX, etc.
In my opinion, much was lost for no gain. At DW, formatting is crippled. Doing so doesn't decrease abuse IMO, it just makes regulars have a blah set of features. And you never know if they're going to be disappeared in the next "upgrade".
There are probably a number of things I've missed, but that's what I can rememer off the top of my head.