Don't be bashful! If you want comments, give comments. You don't need to be an expert photographer to express your opinion about the work of others. You don't need to go into great depth. A simple remark about cropping, composition, color, subject matter, etc. can be of just as much help to a budding photographer as an in-depth critique.
Architectural style is what gives a town or city its character, ranging from the high-rise buildings of Manhattan to the simple adobe structures in Santa Fe. As with landscape photography, you must decide what it is about a building that appeals to you, and what makes you want to photograph it. Think about what qualities you want to emphasize, and then look for the vantage points and light that will help you portray these features.