http – Which special characters are safe and unreserved to use in the complete URL?

After reading these answers and some Googling I couldn’t find a precise answer. RFC states that these characters are unreserved

"-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"

How can . be unreserved? Isn’t that the base of a domain? eg.

Further, it is mentioned in the same RFC that these characters are unwise as some services might use them as delimiters. I’ve never seen these being used in such s way. Have I just not been paying attention?

"{" | "}" | "|" | "" | "^" | "(" | ")" | "`"

My intention is to build a redirect service which would anonymize resources. say I want to generate these 10 char random strings without causing misinterpretations on the receiving side, which could really be anything. I close to understanding until I read the period is unreserved.

I hope someone can shed some light on these as I am thoroughly confused as what’s safe and what’s not