There's a trend that I've been seeing lately both in Webnovel and here that people post translated (poorly, mtl quality) stories as theirs and have the gall to request donations to their patreon as well, is it possible to block them or cancel their accounts?
Press the report button on the series.
In the box that pops up asking the reason, put "Translation" and a link to the original or a similar resource that can prove this.
Strictly speaking, translations are prohibited by the terms of service, but it can be very difficult to tell.
More than a few real authors around here write so poorly that it actually seems like machine translation when it is in fact an original work.
Hence the requirement for strict proof.