Breakdown of По-моему, это очень странный обычай.
это
this / it is
очень
very
странный
strange
по-моему
in my opinion
Questions & Answers about По-моему, это очень странный обычай.
Why is По-моему written with a hyphen?
This is a special type of adverb. When you create an adverb expressing manner or opinion from a possessive pronoun (like мой or ваш) using the prefix по-, it must be written with a hyphen. It evolved from the phrase по моему мнению (according to my opinion), but as a standalone adverb, it always takes the hyphen: по-моему.
Is the comma after По-моему mandatory?
Yes! In Russian, introductory words that express an opinion, attitude, or source of information (like по-моему, по-вашему, or кажется) must always be separated from the rest of the sentence by a comma.
Why use это instead of этот if обычай is a masculine noun?
Because это here acts as a standalone pronoun meaning "this is" or "that is". If you were saying "this strange custom is...", you would use the masculine modifier этот to match the noun (этот странный обычай...). But since you are pointing out a concept and declaring "This is a strange custom", the invariant это is used.
Does обычай decline like an adjective?