Slitherine

Watching a MP game on youtube (https://www.slitherine.com/forum/viewtopic.php?t=117713) it struck me that the text for vasalisation is misleading. Carthage is asking Mauretania to become *their* client-state. Grammatically "their" points to Carthage, but its difficult to read.
I would suggest a rephrase to
Carthage is demanding Mauretania to become a client-state.
or
Carthage is asking Mauretania to become a client-state of Carthage.

After having clicked the wrong one at game start, several times, seen other players asking questions about what happened to their vassals as they accidentally vassalized themselves, seen one with Empires and Kingdoms recently.

Yep I did this and made Ptolemaic Egypt a Client State of Rhodes (on accident-wanted it the other way around). Almost did it again later...but caught myself haha.
Lots of other folks told me they have done the same too...I think the wording is the prompt.