Why is "Ohev Pesha Ohev Matzah"?
Rashi: One who loves to sin against his friend, he loves to quarrel.
R. Yonah: This is put next to the detriment of Arvus. One who loves Matzah (quarreling), he loves sin, for anger begets many sins - "u'Va'al Chemah Rav Pesha" (29:22).
Malbim: Matzah is a great feud with hitting. One who loves it, either (a) he loves sin - "u'Va'al Chemah Rav Pesha" (29:22), and via anger he comes to Matzah - "Rak b'Zadon Yiten Matzah" (13:10). Or, (b) he loves feuds due to his great pride. He thinks that he is higher than the entire nation.
What is the meaning of "Magbi'ah Pischo Mevakesh Shaver"?
Rashi: This refers to pride, like "Shemor Pischei Picha" (Michah 7:5).
R. Yonah: This is like "Lifnei Shever Ga'on" (16:18). Our verse weighs two bad Midos - loving quarrels and sin, and loving authority - and decides that the latter is worse. The primary detriment of feuding is the sins that result from it. Authority itself is despised; those who possess it are broken. It says about pride itself, without seeking authority, "To'avas Hashem Kol Gevah Lev" (16:5). The payment and vengeance "Lifnei Shever Ga'on" is for one who seizes authority.
Malbim: This is one whose house is built in a low place. He raises only his opening. He will be broken when he enters and leaves. So a lowly person who opens his mouth with pride above his level, he will be broken.