It’s interesting to watch how something can become a ‘truth’ just because ‘everyone’ is doing it. One of the things that a lot of bloggers are adapting to: Squeezing two different languages into the same post.
Typically in the Nordics, for example, you would have your native language first, then an English summary at the bottom.
The bloggers I talk to tell me it’s to get a broader audience and to please their international readers. Fair enough.
It’s important to realize what you are sacrificing, though. When you mix two languages on one page, Google gets confused. It doesn’t know how to index you, causing you to drop dramatically on the search results.
Sure, the people that already found you can understand you. Unfortunately, new people will be unable to find you via the world’s biggest search engine and traffic driver.
My advice would be to go all-in to one target group – Local or International.
If you want both, create two blogs. You’ll have two different audiences that expect to be communicated with in slightly different ways.