Shaving specifically for a meis

I've seen this before, and it does seem to make sense on a peshat level based on the pesukim in Torah as well as various pesukim in Nach, but anyway, this is propounded by Shadal as peshat, after Ibn Ezra. The pasuk in perek 19:

כז לֹא תַקִּפוּ, פְּאַת רֹאשְׁכֶם; וְלֹא תַשְׁחִית, אֵת פְּאַת זְקָנֶךָ.	27 Ye shall not round the corners of your heads, neither shalt thou mar the corners of thy beard.
כח וְשֶׂרֶט לָנֶפֶשׁ, לֹא תִתְּנוּ בִּבְשַׂרְכֶם, וּכְתֹבֶת קַעֲקַע, לֹא תִתְּנוּ בָּכֶם: אֲנִי, יְהוָה.	28 Ye shall not make any cuttings in your flesh for the dead, nor imprint any marks upon you: I am the LORD.

Note the context. Ibn Ezra here writes:

[יט, כז
וטעם להזכיר לא תקפו פאת ראשכם –
כמעשה הגוים להיות מובדלים מהם ואחר ששיער הראש והזקן לתפארת נברא, אין ראוי להשחיתו.

ויש אומרים:
כי זה הפסוק דבק עם ושרט לנפש, כי יש מי שישחית פאת ראשו גם פאת זקן בעבור המת.

and later in Emor, in perek 21, by kohanim, where the context is also for a dead relative:

א וַיֹּאמֶר יְהוָה אֶל-מֹשֶׁה, אֱמֹר אֶל-הַכֹּהֲנִים בְּנֵי אַהֲרֹן; וְאָמַרְתָּ אֲלֵהֶם, לְנֶפֶשׁ לֹא-יִטַּמָּא בְּעַמָּיו.	1 And the LORD said unto Moses: Speak unto the priests the sons of Aaron, and say unto them: There shall none defile himself for the dead among his people;
ב כִּי, אִם-לִשְׁאֵרוֹ, הַקָּרֹב, אֵלָיו: לְאִמּוֹ וּלְאָבִיו, וְלִבְנוֹ וּלְבִתּוֹ וּלְאָחִיו.	2 except for his kin, that is near unto him, for his mother, and for his father, and for his son, and for his daughter, and for his brother;
ג וְלַאֲחֹתוֹ הַבְּתוּלָה הַקְּרוֹבָה אֵלָיו, אֲשֶׁר לֹא-הָיְתָה לְאִישׁ--לָהּ, יִטַּמָּא.	3 and for his sister a virgin, that is near unto him, that hath had no husband, for her may he defile himself.
ד לֹא יִטַּמָּא, בַּעַל בְּעַמָּיו--לְהֵחַלּוֹ.	4 He shall not defile himself, being a chief man among his people, to profane himself.
ה לֹא-יקרחה (יִקְרְחוּ) קָרְחָה בְּרֹאשָׁם, וּפְאַת זְקָנָם לֹא יְגַלֵּחוּ; וּבִבְשָׂרָם--לֹא יִשְׂרְטוּ, שָׂרָטֶת.	5 They shall not make baldness upon their head, neither shall they shave off the corners of their beard, nor make any cuttings in their flesh.

Note how the context from the earlier pesukim is for a dead relative, and once again how it is juxtaposed to making cuttings in the flesh, which in Kedoshim was specifically for the dead. Ibn Ezra there writes:

[כא, ה]
לא יקרחה קרחה בראשם -
על המת.

ופאת זקנם -
על המת כמנהג מקומות בארץ כשדים והנה התברר פירוש את פאת זקנך.

וטעם שרטת –
אפילו אחת וכבר נזהרו ישראל על אלה.
וטעם הזהירם כי ראש מוקרח וזקן מגולח ובשר שרוט, לא ישמש לפני השם.

So it seems that on a peshat level he endorses it being specifically for a meis.

Shadal, too, writes:

ולא תשחית את פאת זקנך : השחתת הפאה נזכרה אצל שרט לנפש מת , וכן בכהנים ( למט הכ " א ה ') ופאת זקנם לא יגלחו ובבשרם לא ישרטו שרת , ועיין הראב " ע שם . והנה לפי הפשט כל ישראל אסורים להשחית זקנם מפני אבלות על מת ולכהנים נאסר אפילו הגלוח , גם הוא על מת.

I will not analyze the pesukim in Nach in this post.

But we accept the Perushi interpretation. However, if someone turns around to argue against certain leniencies in Chazal, or later rabbinic interpretation of Chazal in this matter -- especially if they do it on the basis of claimed readings into pesukim in Tanach (... and I am not talking theoretically here) -- well, then we can appeal to this peshat level. We stand here in action based on Chazal and their interpretations, and the Rishonim and Acharonim and their interpretations, and if you want to undermine some interpretation to impose a stringency, we could undermine it all the way until we have massive leniency.

Thus, Baal HaTurim has a derasha about scissors vs. razors, a distinction found as well in the gemara. He notes that the gematria of וְלֹא תַשְׁחִית is zehu taar velo misparayim. This is useful, especially as he is also a halachic authority. Meanwhile, Aharon ben Yosef the Karaite takes pains to explain וְלֹא תַשְׁחִית as with any tool, whether a razor or a scissors.