For context, I use quickcast (on key up) for all of my abilities/items except for TP scroll. Because of this, double-tapping keys to self-cast doesn't work, so I use the option to hold alt for self casting.
This works great 99% of the time, but there's a caveat: non-targettable spells/abilities (phoenix ult, blademail, BKB, etc) can't be self-casted like that, as you just get a "no target" error. This causes quite a few misplays, as I'll be doing something such as playing Legion, and holding alt to self-cast my Press/Mjollnir/BKB/whatever, and then go to hit blademail or phoenix egg without aghs or something and hear a sad sound and nothing else.
This small little change would help a ton with muscle memory, and will also definitely prevent some bad situations on heroes like legion and phoenix (because of the aghs) like I mentioned, and probably other situations that I'm forgetting about. And it's not like it'd be inconsistent; the no target abilities are basically just self-targetted anyways.
Source: https://www.reddit.com/r/DotA2/comments/sj0uzx/a_major_quality_of_life_change_that_id_love_to/
