I am creating a directional sign for an apartment building "Units 1-5 (arrow right) Units 6-10 (arrow up)". If I make the arrows the same weight as the text they do not stand out very well. Is it bad form to make the arrows a heavier weight?
Some big design principles are:
(There's more but these are the ones I find apply the most in this particular case)
Contrast would entail the weight as well as color. Playing around with these principles helps separate one element from another.
My biggest point is: play around with the design. Try different things and pick the one that looks/feels best. Obviously we're not going for anything "artsy" in this case but rather something informative, so keep in mind that people should be able to simply glance at it and know all the information they need to know.
And to answer your question, no, changing the weight is not bad form. However, do make sure that the decision you make still looks good and conveys the information well of course that's subjective, but you're the designer -- but take it around to others and ask what they think (if you have that option).