(I disagreed with the existing answers, so wanted to add my own, but I upvoted them as I think they are valid viewpoints even though I don't agree!)
I'm aware I am making a few assumptions here:
- I'm assuming you are quite early in your career (is it your first 'career' type of job?) from some of the comments you made about maybe starting a family 'someday' etc.
- I'm assuming you are in the UK or other Commonwealth english-speaking country, specifically not in the USA, due to your spelling of the word "labelled", references to 'maternity leave', etc.
Your situation isn't standard in companies
In short... the kind of behaviour in Case 1 and Case 2 as you described them... aren't normal for most companies. They are pretty dysfunctional behaviour.
In Case 1 (I commented on your Q to ask for clarification) it seems that the team (and I use the word 'team' quite loosely!) continued to assign work to someone who was medically excused from work for the moment, then remained silent in sprint review meetings when asked about that subject, presumably to "show up" the absent team member.
What a weirdly passive-aggressive thing to do! I could sort of understand one passive-aggressive inclined person doing something like this, in a misguided kind of way. But this was an orchestrated act as a team. I'm not sure if that is passive-aggressive or just plain mobbing actually.
(BTW in genuine Scrum this shouldn't be able to happen, because each Scrum team member 'voluntarily' commits to take on particular tasks during the sprint.)
In Case 2 (maternity leave) have you asked yourself why it is that a junior colleague told clients she had left the company?
A frame challenge...
As such I think you are asking the wrong question in your circumstances (but I agree it is a good question in general!) because of false assumptions. To put it in user story terms you are essentially asking "As a person with commitments in life outside of the company... I want to prove my value to the company... So that I am considered on equal terms with the 'careerists'."
And that is a valid question, I don't deny it! But I am answering in the context of the additional info you provided. In most normal companies what would happen is that a month or a few months here and there in a few years long career would be covered for, handled by management, and accepted as a normal part of business.
It seems to me that there's a kind of "Hunger Games" (I've actually never watched it myself, but I know what it is through pop-culture) dystopian culture at your company in which resources are scarce, everyone is in competition with each other.
Search out "scarcity mindset", e.g. the link below. It's a situation of believing that there's only so much to go around so 'peers' are competitors, essentially.
These kind of cultures sometimes develop spontaneously but are typically due to some event in the past (like surprise mass layoffs) influencing the way people think of their colleagues (collaborators or rivals for "the few jobs we have remaining"...)
The responses you've described in your Case 1 and Case 2 are not normal in most workplaces, as I said. Case 1 is just plain wrong. Case 2 depends on interpretation -- it's not unreasonable to go through someone's hand written 'rolodex' to find contacts if the person was not so good at keeping centralized electronic records. But saying to clients that Person 2 had left the company (what?!) is not normal and is unacceptable.
It seems to me that here you have a situation where for whatever reason (and if you think about it, you can probably identify the reason) people are constantly in competition with each other, undermining other colleagues at every opportunity, maternity leave (etc) is an opportunity to be seized upon rather than just covered for a few months in a mildly inconvenient way, etc.
I did find it striking that in the cases you described it was "junior" people undermining someone senior to them, in order to discredit them in some way.
I wonder if that's the only way people are able to move up in this company? Not by the honest route of proving themselves through increased knowledge, project exposure, value to multiple teams etc.. but instead just by discrediting someone else so that they can be promoted in the person's place? (And I wonder how that will end for them when they inevitably have to take time off for maternity, mental health, a broken leg, or whatever it is?!)
I'm sorry it isn't a neat answer in terms of "here are some steps I can do" but I would suggest really looking inside whether this company is dysfunctional about that, do you want to continue to work in a place like that and so on.