Ibn Ezra here writes:
and later in Emor, in perek 21, by kohanim, where the context is also for a dead relative:
So it seems that on a peshat level he endorses it being specifically for a meis.
Shadal, too, writes:
I will not analyze the pesukim in Nach in this post.
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.
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.