Short answer: The rule about consonant mutation does not generally apply to single-syllable root words. For example: açız, eti, sütü, üçüncü, etc (= we are hungry, the meat, the milk, third, etc.)
But a small warning: You will encounter some exceptions, as well as words that may LOOK mutated but have a different meaning. For example: at→atımız (horse→our horse) vs. ad→adımız (name→our name)
Hope that helps :)
I found a slideshare that very comprehensively breaks down some of the exceptions to the consonant harmony rules. You'll find an entire section called "Turkish Consonant Harmony Sequence" on slide 8. The exceptions to the rules are on slide 9. You'll find it in a slideshare titled, Linking Verbs in English & Turkish by Yüksel Göknel. I just stumbled upon it recently. Hope it helps.
It is no longer hosted on that website, but I managed to find it elsewhere, where it is available for download as pdf.
also check out the 'recommended' section on the right for lots more turkish grammar guides!
How common is it for natives to omit pronouns such as in this sentence?
In English, we can omit pronouns in some cases where the subject is implied, such as when giving an answer to a question, but hardly ever when constructing a full sentence. Examples:
"What is that thing?"
"What are you doing?"
"Eating a potato."
I suppose it's the same idea, or slightly more nuanced in Turkish?