Balancing deadlines VS quality work at job

Was going through the code quality course where Alex talks about handling edge cases and self-commenting PR's to encourage healthy discussions etc. These are all great for quality work, but I remember in my past internships in these "tricky" implementation parts, instead of self-commenting I would secretly hope no one brings that up so that I could land the PR fast and move on to the next task in the current sprint. This behavior originated from the pressure of completing all tasks assigned in the current sprint.

What's a sweet spot between balancing quality and deadlines? I also enjoy having discussions with other engineers, but the fear of not being able to complete other tasks within the deadline keeps me from pursuing these healthy conversations.

I also have another question (this is my first full time job so i don't really know) - my company offers unlimited sick days off. If I call a day off due to sickness, will I still be expected to complete all my sprint tasks within that sprint? by let's say working extra hours later.