While designing levels for my upcoming 3D platformer, Computer Virus Simulator (you can find out more here and here), I'm trying to make it both appealing to regular players, who don't want to skip content accidentally or get out of the map by accident, and speedrunning community who want to do this.
Sounds impossible? Well, yes and no. Doing that sort of thing requires careful balance between making sure you can't accidentally get out of a level or skip over large portion of it, but if you really, really, REALLY want to do this, you are able to.
To that end, I leave small imperfections in the levels I make that allow dedicated players skip over things or get out of a level in some cases. On the other hand, I need to put these things in non-obvious areas (non-obvious as in "why would you even go there/do that") so players that want complete the game honestly and not as fast as they can, won't trigger these by accident.
As for what these imperfections might entail, it's many things, really. Sometimes it is slight imperfection in the spacing of some seemingly impassable objects that allows a skilled player to force the game's character through it using a close dash, sometimes it's invisible spring object hidden somewhere in the corner that launches player halfway across the level.
Another thing that is important for speedrunners (or people who just have hard time with certain level and want to move on to other, so really both sides of equation) is some sort of level select so speedrunners can work on specific area without going through previous ones first. To that end, I've decided that you'll be able to play all the levels in any order you want right from the start. Yes, there will be suggested order and "completed" levels will be highlighted, but you'll be able to skip over if you really don't want to play specific level.
Back on the level design side, it's important that you also add some hard to access (but not LONG to access, given you have skill) shortcuts for speedrunners that would be of no consequence to regular players and preferrably hidden.
Hopefully this post will be helpful for someone with similar issue.
Please note as well, that while Computer Virus Simulator is a 3D Platformer, these tips apply to any game, no matter of the genre.