Wikipedia:It should be noted

If something should be noted, then just note it. Do not note that the item you wish to note should be noted:

It should be noted that Beethoven was deaf when he wrote the Ninth Symphony. ☒N
Beethoven was deaf when he wrote the Ninth Symphony. checkY

The use of "It should be noted that" here is unnecessary. We are not teaching content, but simply describing it. An article should present important information without explicitly stating which information is important.

"It should be noted that" violates the Wikipedia Manual of Style guidelines MOS:NOTED and MOS:EDITORIAL. The variations "remember that", "note that", and "note:" are direct instructions to the reader, additionally violating the style guideline MOS:YOU. This kind of writing also runs afoul of the WP:No original research policy, in attempting to steer the reader to particular interpretations and conclusions.

Sometimes this phrase is a misguided attempt to sound authoritative. It is also often used to draw attention to information added as an afterthought, such as in a "correction" by a different editor. This can be a sign that the material should be rearranged and rephrased so the crucial information is introduced sooner and more integrated into the description.