It is very good practice to fix all the errors and warnings produced by latex when compiling a document. Systems such as Overleaf and TeXShop often appear to compile the document anyway, but this is short-term bad thinking as many of your collaborators will use different systems.
Some of the warnings are important and having too many will hide the important ones away. This will not be good for you in the long term.
The eagle-eyed will notice that space between words is a different length to that between sentences. LaTeX distinguishes-interword space from inter-sentence space by observing the full stop characters. So an inter-sentence space is placed after every full stop. However, there are exceptions and places where this is wrong.
\@. instend of a simple .I. W. Phillips. Here put a \
between the . and the following space. This indicates that this should
be an interword space. You can also use a ~ (tilde) character which
makes the space the same size, but prevents a line break occurring at
that point, which is often useful.