If the file host turned on “Quota Sharing”, then a portion of all others’ download will subtract from the host’s quota. This is why people says “Please import”, and why sometimes you can download more than 5GB. MEGA "Import Before Download" - Still a Thing? - #8 by Falafel
Adult content is generally okay on there, but it is confirmed that they they act on Lolis and Furries and possibly some other niche genre (BDSM? Rape? Scat) to comply with New Zealand law. They shut down accounts without notice and doesn’t let you retrieve your data.