I think therapy can look very different depending on modality. Classic Psychodynamic T's are all about the therapeutic frame (same time every week, very little by way of personal disclosure, fairly clear, firmly held boundaries). T's who are person centred are all about the relationship (offering a therapeutic relationship empathy, congruence and positive regard) - depending on their practice setting they might be more flexible in some areas - or not etc etc. I'm generalising massively here but you get my drift.

I honestly don't think there can ever be a fixed rule book about what is and isn't ok, more that different T's will work for different people at different times. My T is very flexible, often runs over session time but all of our work happens in session. I contact her only for scheduling but if I need an extra session she'll always try to accommodate me. She does share a little of her day to day life but not so much that it distracts from my work. I couldn't work with someone who was very rigid about time and also couldn't work with someone who gave nothing of themselves at all but others might feel very safe with tight boundaries and a blank screen.

I think there are T's who inadvertently or purposely foster dependence by encouraging or insisting on between session contact, initiating use of touch, being overly affectionate etc and I do think that's less appropriate because it can really blur the lines between professional and personal where therapy potentially turns into a paid for friendship or parenting thing that can be very hard for the client to leave. In my view that feels exploitative. The boundaries keep both the T and the client safe, they don't need to look exactly the same in every relationship but they should be consistent within the relationship, if that makes sense?