@aseriesofstillimages
I checked the guidelines, the use of cis is not forbidden, though it can be reportable if used in a specifically offensive or hostile way (like if I referred to someone here as being cis, knowing they find it offensive).
The convention on this board is to only use cis when referring to a person or group who you know to use it, in order to avoid misgendering those who may to you appear to be cis but do not in fact identify that way and may find it offensive.
So for example, 100% OK to refer to yourself as cis...you should know! Talking about an individual friend or public figure who has identified as cis is again entirely defendable.
Moving on to larger groups is shaky ground...you might have to defend why you feel confident the women you are talking about identity as cis. An example here might be that female women in an explicitly TWAW group like Stonewall can probably be assumed to identify as cis, but women in most other contexts like, for example, the female staff in a supermarket probably should not be.
Statements that divide all women into cis and trans, implicitly forcing cis identity onto every female person who has not actively identified as trans, will be robustly challenged, as will statements like "but cis just means not trans" which is only valid if you accept the implicit underlying belief that womanhood is mental rather than physical, again forcing a gender identity onto others.
Describing a specific individual, especially a poster on here, as "cis" when they have not told you they identify as such, and may even have asked you not to, may well be reported and deleted. To women who do not believe their womanhood is simply a mental difference between themselves and those who identify as men, being called "cis women" is as offensive as being called a man is for a trans woman.