I am solo modding a game that nobody else runs, but I would like to have the proper rules in place in case that ever changes.

What is the general consensus on people submitting IL WR split times that happened during full game runs?

As long as the IL during the full game run follows the established IL rules it should be fine.

It depends, if the ILs in full game match what would occur through a mission select, then it's usually fine. If there's carry over of any objects, health points, gear, etc from a previous level, then its generally not tracked on the IL board.

I'd also suggest to leaderboard mods that they set rules that would allow users to submit ILs from within a longer run.

Usually I try to designate start and end times that:

• Are a clearly repeating on the user interface (an icon appears, a certain sprite appears, a screen appears)
• Also occur when a user restarts the level from the level menu
• Occur within the level and not on a level select page
• Can be used as timing rules for both full game and individual level

For instance:

• Cat Bird: Time begins on the first frame that Cat Bird hits the ground after starting or restarting the level. Time ends when you lose control of Cat Bird at the portal (which is indicated by a black frame in most runs).
• Frozen Free Fall Icy Shot: Time begins on the first frame of your first shot on Level 1 (when the total amount of snowballs you have goes down by 1). Time ends when your ball count hits 0 after beating Level 30.
• Super Cat Bros: Time will start on the first frame that the cat opens its mouth to meow and ends when the facial expression changes when hitting the finish line.