I've a coworker this year and recently we've become close friends. During the workweek, texting almost the entire week, generally work related but also just casual smalltalk, as well as deeper, more personal things. Used to spend quite a bit of time in one another's offices but decided to limit that so as not to give impression of favoritism. Still, end of day, as we both almost always work late, usually for 45m-1hr will sit and chat about things, discuss how we enjoy spending time together, etc. Bit of a routine, surely. Typically, coworker will not go to work events without me being there.
Weekends, there is very little communication. Not zero, but I personally try to give space to people and they are of the opinion "it gives more to look forward to on Monday." In terms of "who initiates," it is fairly balanced. At the start of the day, it's usually them. After-hours, I would say more typically myself. Although we also both work late, so much of the time, as mentioned, it's just one long, ongoing chain day-to-day. Regardless of texting, I know the "end of the day" talks are basically a given, and, even on days where remote work was more convenient, they have chosen to come into the office to have a chance to maintain the usual. We do not discuss attraction/romance/anything inappropriate other than simply valuing each other greatly.
I normally feel that I have a pretty good read on this sort of thing, but there are just some strange mixed signals I pick up on, and the fact that there seems to be an obvious emotional connection but little-to-nothing in the way of flirtation is confusing. I am not really in a position of pushing it toward anything, more just curious what others think. Not concerned with office policies as it's more of a hypothetical curiosity than anything.