Depending on the text based RPG, the view on OOC communication varies wildly. In some RPIs, it is considered extremely bad form and possibly even explicitly against the rules to break immersion by communicating. In most MUSHes, it's considered very standard for players to use ooc to arrange scenes and even map out storyarcs without any kind of organic RP whatsoever. We have a middle approach, but there are some forms of ooc that are expressly forbidden.
1. Harassment is obvious, talking to someone when it obviously isn't welcome. Players have the ability to block pages, but it's still not okay, and rudeness or incivility is bannable.
2. OOC pressure, and this is the one that many players don't think so. For example, Steve knows Bob is trying to kill his character based on excessive, problematic ooc communication. He sends Bob a page warning Bob that if he tries to do this, he has friends that will definitely get revenge, trying to intimidate him out of it. Fucking Steve should not do this. Nor should Stevette send a page full of sad face emoticons to a friend in pages when she finds out Bob is RPing with a romantic rival. These are forms of ooc pressure and emotional blackmail that are intensely problematic that poison a positive RP environment, and players that show a pattern of this will be asked to leave.
Generally speaking, I would vastly prefer players not to discuss their RP plans at all. The problem usually is when 'friends' discover that a story will be curving in a way that they don't want, and make it privately clear that they hate this. This introduces an element of ooc hostility into RP that would otherwise not be there, and means any kind of IC action is then taken as an ooc slight. It's far better to just avoid that entirely.