@Patur Aval Assur
you’re bringing a remote example of an inference you say one would make from what the mishna brura omits.
What you’re talking about is a personal svara, and until they speak to a rav to make sure their svara isn’t flawed, they cannot and don’t pasken.
There is no such thing as anyone who’s not a rav, paskening for themselves to or to not wear tecehiles. Most people aren’t familiar with all the intricacies of hilchos tzitsis, and any argument either side gives is most probably flawed, because they do not know even slightly what their talking about, and at the end of the day they don’t wear techeiles or do wear techelies based on their respective gadol’s custom, not because of their idiotic arguments.
I’ll give you a contemporary example of paskening yourself. The rema says that during sefira, you can take a haircut on friday before sunday lag ba’omer, for the honor of shabbos. Now, someone who is holding ‘second half’ of sefira, who can haircut on shloshes yemei hagbala (this sunday) will use the parallel logic to pasken that they can haircut today, on friday. But in reality, it’s a machlokes haposkim, and the world is machmir in most cases.
The bottom line is, if it’s explicitly in the arcuh hashulchan, or the mishna brura, you can pasken from it. but because so much more is encompassed than meets the eye, and it takes a real posek to determine unwritten halacha, No one ever just paskens for themselves. EVER.