The symbol is very limited and more likely to cause a masquerade breach than to prevent it.
The symbol only works if it is legible. It will get you past the security guard, but dashcams, CCTV and other cheap compliance tech will make you look like a ghost by Louis Vuitton. People could also be too far away to discern the symbol, or simply hear your footsteps and the sound of breaking glass (and blast you with a shotgun through the door). If your target is important enough for the police to care, they may come to the conclusion that mind altering chemicals are involved, and the hunt is on.
You can't use the symbol to live the good life either, because making something uninteresting only works against people who are not paid to care. You could buy out a building and put your rune on every wall, but people working in urban planning know there is a building there, and they know it has electricity, so someone is going to want to come to your doom fortress and read the meter. If the rune makes them not want to do their job, they get fired and replaced with someone else whose first task is to come to your building and read the meter.
The symbol may need a redesign because it does not solve any immortal problems and only removes risk.
Immortal life is tough for reasons unrelated to being seen physically. Not having an identity makes it very hard to exist in society and you can't put your symbol into a database record on a government server. 89
You will have to live in a squatted or condemned house, drive a junker car (make sure to never get into an accident) and steal your clothing. You can do these things without the symbol, it just makes you less likely to get caught.
And therein lies the problem with the symbol. It does one very specific thing, which is to stop anyone from arresting you. It is extremely easy to break the masquerade if you actually go out and try to have an adventure or live a proper life, but there are no consequences to doing so.
I would change how the symbol works entirely. Perhaps consider changing it to a name instead of a sigil, so it can be put into a database and the government will leave you alone. Names, especially unpronounceable 40 letter truenames, are harder to read off a bedsheet, so while the police may have trouble with the paperwork part of arresting you, they could most likely still shoot you. And because you could build up a life as an uninteresting person instead of having to live as a vagrant, you now have something meaningful to lose if you use the ultimate escape plan of hiding in a warded box for 50 years. 89