@ RGPANSN
“A person can always be machmir above and beyond the community standards…however, it should be done in a private manner”
I’m glad you pointed out that qualification from מקום שנהגו of not being machmir in public in a place where the custom is to be lenient.
Here are a few more qualifications
1) Have you heard of a concept of yuharah? Not everyone can just opt to be stringent.
2) There are two reasons given in the Poskim as to why one cannot get a heter for something another Rav forbade, one of them is kavodo shel rishon. This reason applies for lenient rulings as well.
3) When being stringent against widely accepted halachic norms one can also run into the problem of being motxei laz al ha Rishonim.
4) The chumrah must not come l’dai kula
5) Even when a chumra does not come l’dai kula directly it is krum to put one’s efforts into something voluntary at the expense of fully fulfilling one’s obligations
6) Someone who takes on 2 chumros that are in direct contradiction is a fool.