Cheating for XP...
A certain user has been "revising" sentences translated by others just by removing the full stop/period at the end of the sentence so they will appear as the last translator and maybe gain XP through upvotes.
I don't see the point in taking credit for other people's translations as gaining XP doesn't necessarily mean you're learning anything, but it is frustrating when you're on my end.
Is there any scope for reporting this kind of activity?
Yes, in the most recent translation, which is displayed by default when you click a sentence to be translated, there is a little flag and the words "Report Abuse".
Also, if there are multiple translations for a sentence, you can click a link to view them all, and beside each translation is a link to report abuse.
You only need to report an abusive person once. After that, they will show up as having been reported on ALL the sentences they translated.
Before I reported them, though, I think I'd check their profile and if it looks like they're making any effort at all to learn a language, I'd write them directly and ask what's up. If they're just some student that's bored and looking to create trouble, though, I'd just report them without bothering to talk to them. But do at least check their profile first.