There's a pretty low threshold for how conspicuous you can make these cues without confusing most people or getting them to make their eyes wide while they try to give you strong eye contact and scrunch their foreheads as if in distress.
That said, as long as they work when you use them, why should you be worried about the asymmetry? Are you worried that they will notice that you use the cues but don't pick up on them and start to think you're not really paying attention to them or something? If so, I doubt this is the case; in my experience people seem to care much more about whether you are picking up on their non-verbal cues than whether you're using the right ones yourself. Whether or not you use working cues, they will tend to be equally annoyed that you aren't picking up on their cues.
Anyway, unless you're interacting with very good friends it isn't as though you could get the people you are interacting with to use a significantly different set of cues; most of this is going to be largely subconscious/habitual to them.
If you use signals that you wouldn't notice then you'll still be able to send the message, even if you have trouble receiving it yourself, and annoyance about you not picking up on their cues will be similar whether or not you do this; so doing this should afford you greater utility than just not using recognizable signals at all.
Holding conversations in person is useful; feedback is quick, and it seems to be much easier to change your behavior as a result of actually talking with people.
Having effective goal-oriented conversations is somewhat difficult. One source of difficulty is a strong tendency to stray from useful talk into entertaining talk. A typical example is the tendency of many (otherwise potentially productive) conversations between rationalists simply wandering into an extended dialog about the nature of existential risk or some interesting philosophical problem, and then stagnating there (potentially treading interesting new intelligence-demonstrating terrain, but not in point of fact getting anything done or refining beliefs in a meaningful way).
If this is what all participants want out of the conversation, then it's great that we've found a community where people can get their kicks in this particular abstruse way. If this is what some but not all participants want out of the conversation, then perhaps the conversation should divide or conclude. But conversations seem to get derailed--either for significant lengths of time, or indefinitely--even when participants honestly want to get things done, and view conversations with other rationalists as instruments to serve their values.
In the interest of getting things done, I (and Nick Tarleton and Michael Curzi, with the tiniest bit of testing) suggest that the rationalist community try really hard to adopt the following norm: when someone else is talking, and the conversation would be significantly better served by them stopping, let them know. Either point out that the topic is nice to think about but unhelpful, that the topic should be considered later rather now, or whatever else the speaker seems to have failed to notice. To help make adoption a little easier, it might be help to choose one person in advance who will have some responsibility to arbitrate.
If a participant disagrees about the relevance of a remark, don't push it--our hope is that such a system could help people who have honestly wandered from the topic pursuing an interesting tangent or happy thought, not to resolve any actual dispute. If a participant doesn't want to adhere closely to any particular notion of usefulness--for example, if someone is having a conversation to simply enjoy themselves and unwind--then the conversing parties should resolve their misunderstanding, or if not possible simply stop talking to each other and save some time.
Have any LWers considered other lightweight measures to hold more useful conversations? There seems to be low-hanging fruit here, and there seems to be a lot to gain.