Polish syntax sometimes really drives me crazy. ... and then I realised: this sentence' structure is the same in Polish and German! I guess my "feeling" of how languages work is highly influenced by English and the Roman languages.
Just as in English "I would like to" is a more polite version of "I want to", in Polish a more polite version of "Chcę" is "Chciałbym" (for a man) or "Chciałabym" (for a woman).
I was taught that you should write "Ci", "Cię" etc with a capital letter at the beginning but I notice this is not something you do on this course. Is there any reason why not? Is it an old fashioned thing that nobody does these days?
You should, if you are writing directly to someone. So if I right know, in this comment, wanted to write "Chcę Ci coś pokazać" to you, I should capitalize "Ci". This applies to letters, e-mails, text messages, Facebook messages, comments... well, simply anywhere where you address someone specific directly.
However, if you open a Polish book, you will see that there is no capitalization in the dialogues, because it's not the author addressing the reader, but just the words said by the characters, written down. Same applies for movie subtitles, etc.
On Duolingo you have contextless sentences, so there's also no reason to capitalize the pronouns.