Things like the two you mentioned are useful as a code standard, but they're also things that junior devs should be learning from senior devs in the process of work anyway. There's no point slavishly following a standard if you're going to never learn from it.
Well, by definition, you've just created a coding standard.
We often just start out using the standard of someone who has thought it through.
Crockford for JS, Microsoft for C# and Google for Java.
If someone raises a complaint, we do consider it but then the onus is on the developer to justify why it should be changed and that means the developer has to have thought out his/her idea, which is what you really want to begin with.
If it's something as trivial as marking members with "_" or "m_" then it will be a non starter due to,as you said, it just doesn't matter as long as your consistent.