Why Chinese use too many 错别字?
The cases you mentioned is more or less like slang. If there is a urban dictionary it would be in there. Some of them are evanescent though. There are several cases I could think why they use those characters.


Funny accent: some people pronounce some words with their cute accent from their dialect. One day these thing gets viral, and popular. like 卧槽，蓝瘦香菇, etc.
Internet sensation: for example, 小白 means beginner, 你是个好人 means sorry I can't say yes to your proposal.


So these words are more common in younger generations I wouldn't say they are wrong. If you use them with old people they would possibly not understand. Also, sometimes we understand them by the context.

I think similar things are in English as well. Like you say Netflix and chill for sex. Sis, bro, bae... too many.

Understand those gets you more comfortable in getting into Chinese contemporary culture for instance if you live in China.