Reasonable and sane behavior of cd. Just get into the habit of always using lower case names for files and directories, that's how our forefathers did it.
Even worse, many components will ignore the XDG_DOWNLOAD_DIR var so even if you manually change it to $HOME/downloads (lower-case) it will often break things.
If a directory has multiple words in it I usually do kebab case: i-like-mine-in-a-way-i-can-read-them-properly. Both easier to read and type than pascal case.
For more complex filenames I use a combination of kebab-case and snake_case, where the underscore separates portions of the file name and kebab-case the parts of those portions. E.g. movie-title_release-date-or-year_technical-specifications.mp4