Well I'm not sure I would call it a "mechanic". It's simply that the ending will be affected by whether you get the pregnancy tag on characters. To be more specific, the planned way endings are going to happen are 2-3 "main" endings, but there will be a reel covering each character's state after the game (Much like you would see in Fire Emblem). This reel would likely reflect pregnancy, and may change depending on how much you progressed through their arc, or relation with them. I figured this would be the most logical way of approaching endings, as the cast of characters has gotten quite large.
Specifics still aren't ironed out, but that is the current plan at least.
Ya, there have been some reports of the spermy icon getting kinda desynced from the actual bar, and going too high with the latest build. I'm going to be taking a look at this in the next build, and hopefully fix it up.
Also ya, when modifiers come in too fast it does that. I may find a way to fix this, but regardless I feel like it's going to be a little weird simply based on the fact when mods start coming in that fast, the game gets kinda wild to begin with ahaha. There are quite a few bugs that came in v0.14, as there were a good amount of changes going on. Thanks for mentioning them though.
Aye, worry about yourself first. If you do decide to support in the future, and Patreon is not something you want to interact with, the full game is coming out on Steam and Itch.io when it is completed. Big Hearts of you pick it up! If not, thanks for playing either way. Glad you enjoyed.