A backup is never a good place to store data because it is designed to recover your system not as an archive.
Also if the Time Capsule is used for backups then storing your own data there is bad for 2 reasons.
First your data stored with the backups will confuse Time Machine when it comes time to delete old backups to make room for new backups.
Secondly, since anything stored in the disk used by Time Machine for its backup can not be backed up.
These are the commandments of data storage
never consider any computer a data storage device, rather a data creation ,sending, and manipulation device. Woe upon anyone who thinks any data is safe on any computer, even copied upon multiple partitions.
Burn important data onto multiple copies of archival DVDs and store same in cool dark fireproof safes, hidden places, secret places, multiple places
always consider and expect your computer’s hard drive to completely crash anytime, at all times, and keep a cloned and updated hard drive handy at all times to return to immediate productivity and avoid program and parameter reinstallation and tweaking.
never back up your data exclusively upon magnetic hard drives or flash storage, nor consider same since magnetic storage degrades over time even under ideal conditions