Based on the last line of the משנה דף מה. “מיד תינוקות
Major Question:
Why is person exempt from damaging in course of simcha when there is a rule אדם מועד לעולם – person is always responsible for damage?
Learn פמ”ג ס”ק ז מוחלין & ס”ק ח פורים אונס קצת
https://hebrewbooks.org/pdfpager.aspx?req=41247&st=&pgnum=363
And see דרכי משה & ב”ח for a different reason
https://hebrewbooks.org/pdfpager.aspx?req=14270&st=&pgnum=560
Halachic Question:
Based on the exemption of Rashi & Tosfos for damages in the course of activities of simcha –
Can one engage in a sport which is liable to cause injury to the opponent?
Is the player exempt from payment for damages he caused?
See טור חושן משפט סימן תכ”א who quotes the רא”ש which discusses someone got injured during a wrestling match.
https://hebrewbooks.org/pdfpager.aspx?req=14270&st=&pgnum=628
The ראש seems to give a few reasons why he rules the person is exempt from paying for damages.
Question:
What is the bottom line reason?
See בית יוסף
See שולחן ערוך חושן משפט סימן תכ”א סעיף ה
https://hebrewbooks.org/pdfpager.aspx?req=9733&st=&pgnum=471
And סמ”ע ס”ק י
Question:
Is there a violation to hurt someone even if the individual forgives the payment for the damage?
Learn רמב״ם חובל מזיק ה, א
and מנחת חינוך מצוה מח אות ג
Learn the גמרא דף מה from after the Mishna until “א”ר אבהו (four lines from bottom of the Amud)
Learn תןס’ “עלה
The ריטב”א has a different understanding than Rashi and Tosfos of the size of the Mizbeach
https://www.sefaria.org/Ritva_on_Sukkah.45a.4?lang=bi
See שפת אמת who summarizes the opinion of the Ritva & for a difference between them in how to understand the pasuk עד קרנות המזבח
https://hebrewbooks.org/pdfpager.aspx?req=14522&st=&pgnum=206&hilite=